Authors:
Oros E., Constantinescu E., Paulescu D., Popa M., Plăcintă A.O.

Abstract:
We present a study of the strongest historical earthquakes (Mw > 5.0) occurred in West Romania between 1900 and 1980 to review and homogenize the Romanian Earthquakes and Focal Mechanisms Catalogues on instrumental data basis. New hypocenters relocation, moment magnitudes, Mw and focal mechanisms solutions are obtained on historical instrumental data basis (seismograms, bulletins, catalogues). The vectorized seismograms were analysed to pick up the arrival times of the body and surface waves after careful identification of the phases as a function of the velocity model, first P wave polarity, amplitudes and corresponding periods. We located the hypocenters of 15 events by a grid search algorithm often using S-P differences instead of absolute times. The magnitude was estimated from displacement spectra by the scalar seismic moment method. The focal mechanisms for 9 events were obtained by polarities and sometimes by full-wave inversions depending on the data quality. The solutions based on polarities data are high quality being constrained through the comparative analysis of the observed and computed waveforms. On average, the P axes are NE oriented (N67OE) like the regional trend of the horizontal component of the stress field and the general orientation of the nodal planes.

Authors:
Oros E., Plăcintă A.O., Popa M., Rogozea M., Paulescu D.

Abstract:
The purpose of the present study is to elaborate a new model of the macroseismic intensity attenuation using all observed intensities data for the crustal earthquakes in Romania and then, based on this relationship, to calibrate the Bakun-Wentworth method, one of the modern methods most used to estimate the parameters of the historical earthquakes (localization, moment magnitude-Mw). The study is based on 14 calibrating earthquakes (4.5 < Mw < 5.7, 811 IDPs, II < Ii < VIIIO EMS) and 7 validation earthquakes (3.5 < Mw < 5.4, 215 IDPs, II

Authors:
Partheniu R., Craiu A., Diaconescu M., Ioane D., Moldovan I.A.

Abstract:
Previous studies have shown that the Black Sea was subject to tsunami waves generation in the past (Altinok, 1999), with a total of twenty-two events generated. According to recent studies of Diaconescu et al. (2008), the Black Sea is divided in nine seismic sources. A more recent approach structures the area in ten different seismic sources, given by Moldovan et al. (2016, 2017). This study focuses mostly on the Istanbul seismic source, which triggered in the past high magnitude earthquakes followed by tsunami waves. The most recent event generated in the Black Sea was on 15 th of October 2016, with a magnitude Mw = 5.1, at a depth of 10 km, with the following location: Latitude 42.19° N, Longitude 30.68° E. The focal mechanism determined through the moment tensor inversion (U.S. Geological Survey-USGS) indicates a reverse faulting type. For this event, few tsunami modeling scenarios were run. When using the exact parameters of the earthquake (Mw = 5.3), the simulations show no results. More simulations were computed, increasing the magnitude with steps of 0.2, from 7.0 up to 7.8. The modeling was accomplished using the Tsunami Analysis Tool (TAT), software provided by the Joint Research Center (JRC) from Ispra, Italy. The results of these tsunami simulations show low wave heights for a magnitude of 7.2, of maximum 0.42 m in Eregli (Turkey), 0.36 m in Zonguldak Eregli (Turkey), and 0.32 m in Kilimli (Turkey). For a magnitude of 7.6, the maximum wave heights are higher, considered to be moderate, of 1.59 m in Zonguldak Eregli (Turkey), 1.21 m in Eregli (Turkey). Moreover, there are three locations from the Romanian shoreline affected, as follows: 0.83 m in Mangalia, 0.5 m in Techirghiol and 0.39 m in Constanţa. In order to obtain a correlation of these simulations to real events of high magnitude, we will compare them with two past earthquakes from the Istanbul seismic area, generated on 12 th of November 1999 (Mw = 7.2) and 17 th of August 1999 (Mw = 7.6). Due to their location inland, the results for these two earthquakes display very low wave heights, of maximum 0.18 m. These events were also modeled using the same software, same methodology, considering as location an offshore position of the earthquakes, assumed as being generated on similar faults. The results were compared to the modeling output of the 2016 earthquake from October. For a better evaluation of the tsunami waves possibility of occurrence in the Istanbul seismic area, more information regarding the parameters of high magnitude earthquakes, their location and focal mechanism type, are necessary.

Authors:
Radulian M., Dinescu R., Popa M.

Abstract:
The paper brings together all existing data related to seismic monitoring in order to characterize the earthquake-prone areas in Romania. A review of previous works on this subject is also carried out. The impetuous development of the Romanian seismic network in the recent years as number and quality of instruments makes it possible today to identify with a high degree of confidence the geometrical configuration of seismicity patterns able to generate strong earthquakes. At the same time, we are now able to separate the tectonic active zones from those contaminated by human activity and to define with higher accuracy the earthquake-prone areas. By increasing the range of magnitude completeness and by assessing specific variations in time and space of seismicity, the paper brings a significant contribution to improve our ability to evaluate seismic hazard in Romania.

Authors:
Țigănescu A., Bălan S. F., Toma-Dănilă D., Apostol B. F.

Abstract:
The purpose of this research is to analyze the data recorded on instrumented structures in Bucharest and adjacent free-field seismic stations during the last moderate earthquake that occurred on 28th of October 2018 in the Vrancea seismic zone. The earthquake had a 5.5 moment-magnitude, a depth of 147.8 km, and it was felt on a large area of Romania, generating very little damage in Bucharest. In the last five years, the National Institute for Earth Physics has deployed permanent instrumentation (accelerometers) at key stories of five buildings in Bucharest metropolitan area that recorded the seismic motion of the mentioned earthquake. Three of the buildings have been equipped with seismic isolators and dampers and the performance of this earthquake-protection system was assessed based on earthquake data. The data recorded by four free-field seismic stations located in Bucharest were used as reference motion. In order to assess the amplification or reduction of the seismic waves when propagating in the structure, acceleration and velocity data were analyzed, both in time domain and in frequency domain, for selected frequency ranges. The paper presents also the acquisition setup, the dataflow and the data-processing methods. This study highlights the amplification / reduction of the seismic signal recorded at the ground level by the building structure. In the framework of previous studies on data recorded on buildings located in Bucharest, this study adds new valuable information and contribute to a better understanding of seismic response of buildings.

Authors:
Toader V.-E., Biagi P. F., Moldovan I. A., Mărmureanu A., Mihai A.

Abstract:
The solar radiation affects the life on Earth and it is important in meteorology, climatology, solar energy, agriculture, hydrology and seismology, too. The Sun warms the earth which reflects a part of the energy. An effect of tectonic stress increases the ground temperature that is radiated into the atmosphere. We study the possibility to use the variation of reflected energy in correlation with seismicity, radon concentration, CO2 emission, ULF radio waves, telluric currents, air ionization, temperature in borehole and acoustic noise. In this case, the solar radiation is a precursor factor. This research is important to study the effects of climate change. Analyzing the solar energy budget we find information about the atmosphere: aerosols, ozone, sulfur dioxide, carbon dioxide, nitrogen dioxide and pollution. Our multidisciplinary network (AeroSolSys) monitors Vrancea, a Romanian area characterized by deep earthquakes. For this study, we use two stations, Plostina and Vrancioaia, where we have a net radiometer and a pyranometer. The first sensor includes two pyranometers (up and low) and two pyrgeometers (up and low), a Pt-100 and a Thermistor. The spectral range covers both the Solar Radiation, 0.3 to 3 micrometers, and the Far Infrared Radiation, 4.5 to 42 micrometers. In this case, we measure and determine the temperature of sensor necessary for pyrgeometers, pyranometer short-wave radiation up and low EyU - EyL, pyrgeometers long-wave radiation up and low EgU - EgL, Albedo, net solar radiation NSR, net far infrared radiation NFIR, net total radiation NTR, sky temperature SkyT and, land surface temperature LST. In Vrancioaia, we have a pyranometer with range 0.3 – 2.8 micrometers and maxim 1600 W/m2. Two video cameras monitor the sky and the measurements are correlated with meteorological equipment installed in each location. We use information about solar activity from NOAA satellites and Copernicus CAMS. The humidity of ground is important in energy budget and it is estimated from meteorological data and telluric currents. The interval of analysis is 3 hours, between 2016.01.01 – 2018.05.31. It is difficult to notice the effect of tectonic stress since the daily and seasonal variations of solar radiation are high but global warming is obvious. Solar radiation monitoring helps us to understand other phenomena like radon emission or air ionization.

Authors:
Toader V.E., Moldovan I.A., Mihai A

Abstract:

Authors:
Zoran M., Savastru R., Savastru D., Mateciuc D.

Abstract:
This paper investigates earthquake precursors which can be detected from geospatial time series data in synergy with ground monitoring data. Have been analyzed air and land surface temperature anomalies, Aerosol Optical Depth (AOD) variations as well as anomalies recorded by outgoing long-wave radiation and latent heat flux from TIR (Thermal InfraRed) from MODIS Terra/Aqua, NOAA AVHRR, Landsat TM/ETM/OLI and Sentinel 1/ 2 data. Also have been located ground surface deformations detected through Synthetic Aperture Radar Interferometry (InSAR) radar satellite (Sentinel 1) and high quality in-situ GPS monitoring data as well as in-situ monitoring of radon in air near the ground for some moderate earthquakes recorded during 2012 – 2016 period in Vrancea active region in Romania. As Vrancea zone in Carpathians has a significant regional tectonic activity in Romania and Europe, the joint analysis of satellite and field geophysical information is revealing new insights in seismic hazard assessment.

Authors:
Diaconescu M., Ghiță C., Oros E.

Abstract:
The Apuseni Mountains are located in the western part of Romania and are limited to the west by the contact with Pannonian Depression and to the east by the Transylvanian Basin. Basically To the south Apuseni Mountains are bounded by the South Transylvanian Fault and in the northern part by the North Transylvanian Fault. Apuseni Mountains represents an isolated massif inside Carpathian arch, consisting of complex folds and thrust belts formed in Cretaceous period as results of interactions between multiples micropletes separated by Tethys ocean branches. The orogenic system of the Apuseni Mountains can be divided in two parts, in fact two main pre-Neogen structural units: The North Apuseni, composed of an early proterozocic Variscan basement belonging to the Inner Dacides as part of the Tisa geodynamic block and South Apuseni as the as aprt of Dacia Block (his northern part) which include a ophiolitic sequence of the Carpathians. The tectonic regime of the Apuseni Mountains consist of two type, such as: a compressive one, according to the tectonic structures, with SH max predominat oriented NW to SE, and in the marginal area is a predominat extensive tectonic regime. For the Mures Corridor (South Transylvanian Fault) the tectonic regime is strike slip type.

Authors:
Dinescu R., Munteanu I., Placinta A., Dinu C., Oros E., Popa M., Radulian M.

Abstract:

Authors:
Ghita C., Diaconescu M., Craiu A.

Abstract:
The purpose of this work consists in analyses of declustering catalogue and seismic sequence recorded in Vrancea crustal area . The moderate-size earthquake with local magnitude 5,7 which occurred on November 22, 2014 in Vrancea region, at 41 km depth, is the largest crustal event instrumentally recorded at the bending of the Eastern Carpathians. The crust seismicity in front of the Carpathian Arc spreads to the East, in a strip delimited by the Peceneaga-Camena fault, to the North and East, and to the South is lost to the Intramoesica fault. The crust seismicity does not exceed the magnitude of 5.6 (Mw) and it seems to have no relation to the seismic activity of the subduction lithosphere. Seismic activity is characterized by spatial and temporal clustering in the Ramnicu Sarat sub-zones through seismic sequences and swarms in the Vrancioaia area. Using the first version of the software SEDA v.1 [1] we determined the Maximum Likelihood Estimation (MLE) ETAS model on an Vrancea area. The algorithm implemented in SEDAv1.0 is an innovative method based on Simulated Annealing. The Epidemic Type Aftershock Sequences (ETAS) model is the most popular stochastic model used to describe earthquake occurrence, to forecast earthquakes and to detect fluid/magma signals or induced seismicity.

Authors:
Mateciuc, N.D., Bălă A.

Abstract:
The studies for Recent Crustal Movements by the aid of space geodesy techniques are integrated into the researches on the Earth?s crust dynamics, as a reflection of the complex geodynamic phenomena that occur in the crust and in the subcrustal lithosphere. In addition to the fundamental nature, the research in this field presents a practical characteristic, competing alongside geology and geophysics to the shaping of new energy sources or solid mineral substances, to the determination of the soil stability degree in inhabited areas or in those in which large industrial targets and utilities are intended to be placed in. The knowledge of movements affecting the Earth?s upper crust, movements that precede, accompany or follow the eathquakes, is also a topical issue. The paper presents some of the most important research projects developed in Romania, which were based on the measurement data obtained exclusively by space geodesy methods. There are presented some of the most significant results achieved in the framework of each research project together with the limitations imposed by the used acquisition technology. In chronological order are mentioned first GPS measurements in Romania, started in 1994, in a network centered on the Dealul Piscului observer, followed by Romania's involvement in a regional geodynamic project, CERGOP and finally a major international project, CRC461, also continued after 2003 with the continuous help of the University of Delft (Nederlands), a project that led to the development of an extended network of GPS permanent stations in Romania, all in operating status and whose results are a valuable support for the geodynamic studies. There are made brief references to the first application of the Finite Element Method in a GPS subnet from the Vrancea extended network together with some of the most important obtained results.The strong earthquakes with their catastrophic consequences, which have taken place in recent years on a global scale, similar to that of 4 March 1977 in Romania, have fully demonstrated the need for the knowledge of these types of crust movements in order to contribute, together with other methods, to solve the very complex problem of the earthquake forecasting.

Authors:
Mihai A, Moldovan I.A., Toader. V. E.

Abstract:
In this study, the anomalous geomagnetic variation related to the moderate Vrancea earthquake (Mw=5.5) on 28 October 2018 was shown. This anomaly and their associated seismicity were analyzed and compared with a similar anomaly which occurred on October 2016-May 2017. To better distinguish the seismotectonic anomalies from external geomagnetic variations (geomagnetic storms), the datasets recorded at Muntele Rosu (MLR) located inside seismogenic zone were compared with datasets recorded at Surlari (SUA) located at 100km away to the seismogenic area. Also, the geomagnetic data were correlated with the daily geomagnetic indices taken from NOAA/Space Prediction Center. During these two anomalies, were plotted graphs with daily and cumulative energy release for every earthquake bigger than Mw>3, occurring inside the anomalies. The anomaly which accompanied the moderate earthquake from October 28 th , 2018 is visible only on By component (EW component) of the local geomagnetic field and this anomaly is looking similar to the anomaly which occurred during October 2016-May 2017. Both of them shows a step-type change in By component and the total decrease measured on By component is around 100 nT. The computed seismic energy during the late geomagnetic anomaly showed low seismic activity in both magnitude and number. The unequal distribution of seismic energy during these two anomalies is explained by the depth occurrence of main shocks. During the anomaly occurred between October 2016 and May 2017, the seismic activity was greater and was concentrated in 90-100 km depth interval. Otherwise, during the recent anomaly, the seismic activity was lower and concentrated in 130-150 km depth interval. In the study of the relationship between geomagnetic anomalies and the occurrence of intermediate earthquakes is mandatory to take under consideration the depth interval where the earthquakes are concentrated. The mechanical response of intermediate depth structure could variate with the depth because the rheological properties of rocks are closely related to the changes in the pressure-temperature domain.

Authors:
Mihai A., Moldovan I. A., Toader V., Partheniu R., Petrescu L.

Abstract:
In this study were used geomagnetic data recorded during last 5 years, from 2013 till present. The records were corrected for missing and wrong data induced by malfunction of the data acquisition system. The main purpose of the paper is to identify the magnetic field behaviour in relation with space weather, meteorological phenomenon including annual/diurnal temperature variation, local and regional seismic activity. The paper is focusing on geomagnetic anomalies detected on the recorded field at one magnetometer located near Vrancea seismogenic zone prior to Mw>4.5 crustal and intermediate depth earthquakes. During these 5 years of investigations one crustal earthquake and three subcrustal earthquakes with a moment magnitude Mw between 5.0 and 6.0, occurred in the Vrancea zone. All three intermediate depth events were accompanied by significant anomalies on Y axis (EW component) of local geomagnetic field measured at MLR observatory. The MLR magnetometer was outside the preparation zone of the crustal earthquake, located at 100km distance from the epicenter, so no anomaly was observed. In order to highlight the anomalies recorded at Muntele Rosu (MLR) seismological observatory, these data were compared with data from Surlari (SUA) observatory, located about 150 Km South-East outside the Vrancea seismogenic zone. Similarly, earthquakes with Mw between 4.5 and 5 are accompanied by same type but smaller amplitude anomalies, were the drop on Y axis was less than 10 nT instead of 20-30 nT as those occurred prior to earthquakes with Mw>5.0. The latter ones are harder to observe during the summer time when these anomalies are hidden by large diurnal variations. The anomaly duration extends from days to sometimes months, without correlation with the earthquake magnitude. To better distinguish the local/regional anomalies from global geomagnetic behaviour, both MLR and SUA datasets were also corelated with the geomagnetic indices from NOAA/Space Prediction Center. The presence of geomagnetic storms creates a specific type of anomalies that sometimes might hide the ones related to earthquakes. The geomagnetic measurements were also compared with temperature values recorded at MLR station both for avoiding wrong interpretation of instrument response related to temperature variations, and to highlight possible correlations of magnetic field behaviour with ambient temperature. The three medium sized intermediate earthquakes that have occurred in the studied time interval provided a good opportunity to investigate the link between the presence of anomalies on geomagnetic records at Muntele Rosu observatory and seismicity in Vrancea zone.

Authors:
Moldovan I.A., Constantin A. P., Ardeleanu L., Ionescu C., Grecu B., Manea L. M., Toma-Dănilă D., Toader V.E., Partheniu R., Manea E. F., Tiganescu A., Placinta A. O.

Abstract:
Romania is one of the most seismic-prone countries in Europe due to the periodically occurrence of strong intermediate-depth earthquakes in Vrancea seismogenic zone. The Vrancea area is located beneath the South-Eastern Carpathian Arc bend, at the contact between the East - European plate and the Intra-Alpine and Moesian sub-plates. An intense seismic activity is recorded in the mantle, within a narrow, almost vertical descending volume between 60 and 180 km depth. Earthquakes with magnitudes larger than 5.0 (Mw) and macroseismic effects exceeding V MSK degrees on extended populated area occur in Vrancea seismic zone, with a return period of around 2 years. Besides the extended scientific studies, the near real time estimation of the macroseismic intensity recently became mandatory for the insurance companies to cover some of the losses and damages that earthquakes might cause to houses, belongings, and other buildings. The first approach to obtain intensity values was to develop an online environment for collecting people feedback regarding the effects of earthquakes and for the automatic approximation of the intensity. The automatic intensity estimation code from the online feedback proposed by [1], [2] and adopted by [3] for the Romanian earthquakes was improved and used for this study. Additionally, there were used prediction equations to obtain intensity values from the epicentral intensity, and epicentral and hypocentral distances. Besides the estimation of macroseismic intensities from online people feedback and from attenuation relations, equations for conversion of peak ground acceleration in macroseismic intensity were also required for a rapid evaluation of ground motion effects. In order to avoid the increase of the prediction uncertainties, the data must be selected in such a way that they represent the parameters’ rank for which the prediction will be accomplished and the selected data must be representative for the investigated regions and seismic source. In this paper were developed conversion methods from PGA to macroseismic intensity for moderate intermediate depths earthquakes with 4.5

Authors:
Moldovan I.A., Constantin A. P., Manea E. F., Partheniu R., Constantinescu E. G.

Abstract:
The macroseismic intensity attenuation and its variation as a function of the epicentral or hypocentral distance is one of the issues in the seismic hazard assessment and of shake map generation. This output is especially required by emergency situation inspectorates or by the insurance companies. The macroseismic intensity investigations are carried out in Romania after all earthquakes with magnitudes larger than 4.0. Starting with 2014 the classical method for macroseismic information collection was doubled by the online method, consisting in online questionnaires and rapid feedback based on pictograms. In the current study the ground-motion prediction equations were computed in terms of macroseismic intensity for Romania, using the large Mw>6.5 intermediate depth Vrancea earthquakes and were tested on the recent moderate events to certify their validity at lower ranges of magnitudes. The mathematical relation proposed by von Koveslighety in 1906 was used for analysing the attenuation of seismic intensity with distance in terms of the difference between the maximum observed intensity, referred here as epicentral intensity Io and site intensity I, for 24 different azimuths. The macroseismic catalogue used in the present study comprises 7461 intensity data points (IDP) for 5 large Vrancea (Romania) intermediate depth earthquakes (10th November 1940. 4th March 1977, 30th August 1986, 30th and 31st May 1990), 471 IDP?s for the moderate 27th October 2004 earthquake and 3048 IDP?s for nine intermediate depth moderate earthquakes (4.1

Authors:
Muntean A., Năstase E., Manea L.

Abstract:
Romania is covered by more than one hundred GNSS (Global Navigation Satellite System) permanent stations, that have been set up over the last seven years, maintained by different agencies and having different technical architectures and scientific objectives. Many of these stations provide support for geo-referencing applications such as surveying, the network being developed by National Agency for Cadaster and Land Registration (ANCPI) and by a private company, TopGeocart. Two networks are developed with scientific purposes: one developed by the National Institute for Earth Physics - NIEP and the other one developed by the National Institute for Research and Development on Marine Geology and Geo-ecology – GeoEcoMar. Several limiting factors were identified in terms of utilization: no site uniqueness, no file redundancy, no quality control or hardwire web service. Our goal is to collect all those GNSS data in order to standardize, perform quality control and harmonize for creating the metadata. We present and discuss step by step all the implementation levels of standard tools necessary for generating, validating and disseminating pre-defined GNSS metadata, tools for the generation and dissemination of metadata. All those will allow the end-users, and in particular, geoscientists, to freely access the geodetic data, derived solutions, and associated metadata using a transparent and standardized process. Finally, we detail the technologies and software that were used and developed to build this e-infrastructure, the system output data and the conclusions derived in terms of data volume, security and usefulness. The involvement in EPOS – IP project as a member of GNSS Data and Products Working Group helps us evolve in the same direction, test and implement GLASS software package for the dissemination of GNSS data & dedicated processing outcomes, time-series, velocities, and strain-rates - to be created using state-of-the-art methodologies for a better understanding and completion of the tectonic puzzle pieces of Solid Earth processes in this challenging structure of Southeastern Europe.

Authors:
Placintă A.O., Popescu E., Moldovan I.A., Radulian M., Mihai A.

Abstract:

Authors:
Poiata N., J.P., Vilotte P., Bernard C., Satriano C., Obara K.

Abstract:
In this study, we demonstrate the capability of an automatic network-based detection and location method to extract and analyse different components of tectonic tremor activity by analysing a 9-day energetic tectonic tremor sequence occurring at the downdip extension of the subducting slab in southwestern Japan. The applied method exploits the coherency of multiscale, frequency-selective characteristics of non-stationary signals recorded across the seismic network. Use of different characteristic functions, in the signal processing step of the method, allows to extract and locate the sources of short-duration impulsive signal transients associated with low-frequency earthquakes and of longer-duration energy transients during the tectonic tremor sequence. Frequency-dependent characteristic functions, based on higher-order statistics’ properties of the seismic signals, are used for the detection and location of low-frequency earthquakes. This allows extracting a more complete (∼6.5 times more events) and time-resolved catalogue of low-frequency earthquakes than the routine catalogue provided by the Japan Meteorological Agency. As such, this catalogue allows resolving the space–time evolution of the low-frequency earthquakes activity in great detail, unravelling spatial and temporal clustering, modulation in response to tide, and different scales of space–time migration patterns. In the second part of the study, the detection and source location of longer-duration signal energy transients within the tectonic tremor sequence is performed using characteristic functions built from smoothed frequency-dependent energy envelopes. This leads to a catalogue of longer-duration energy sources during the tectonic tremor sequence, characterized by their durations and 3-D spatial likelihood maps of the energy-release source regions. The summary 3-D likelihood map for the 9-day tectonic tremor sequence, built from this catalogue, exhibits an along-strike spatial segmentation of the long-duration energy-release regions, matching the large-scale clustering features evidenced from the low-frequency earthquake's activity analysis. Further examination of the two catalogues showed that the extracted short-duration low-frequency earthquakes activity coincides in space, within about 10–15 km distance, with the longer-duration energy sources during the tectonic tremor sequence. This observation provides a potential constraint on the size of the longer-duration energy-radiating source region in relation with the clustering of low-frequency earthquakes activity during the analysed tectonic tremor sequence. We show that advanced statistical network-based methods offer new capabilities for automatic high-resolution detection, location and monitoring of different scale-components of tectonic tremor activity, enriching existing slow earthquakes catalogues. Systematic application of such methods to large continuous data sets will allow imaging the slow transient seismic energy-release activity at higher resolution, and therefore, provide new insights into the underlying multiscale mechanisms of slow earthquakes generation.

Authors:
Dinescu R., Rogozea M., Popa M., Chircea A.

Abstract:
The most important products of the seismological network are complete and reliable earthquake catalogs. Detecting earthquakes over an extended scale, from smallest magnitudes to large events is a critical issue in many studies, such as earthquake statistics, source seismology and seismic hazard. During the last years, the seismic network of Romanian has developed by increasing the number of stations and station coverage. Despite the significant improvement, the coverage is still not uniform all over the Romanian territory due to some natural limits (geographical borders, topography, etc.). Because of this, the monitoring and localization of local seismic events with low-magnitude using routine detection and localization methods is sometimes difficult and may lead to considerable magnitude or location errors. Recorded data affected by errors and quarry blasts recorded as seismic events (earthquakes) in the Romanian earthquake catalogue (ROMPLUS) will distort the seismicity pattern characterizing a specific region. The goal of this study is to increase the capability to detect and localize low-magnitude seismic events in the south-eastern part of Romania (Dobrogea region) by applying the cross-correlation method for 2012 – 2016-time interval. To this aim, we selected six templates for events recorded both during working hours and during night. The waveform similarity analysis was performed on signals recorded on the vertical component of the seismic station Targusor (TIRR), a high-quality station operating in the study region. The waveforms recorded for template events are cross-correlated with successive windows from the continuous waveform recording along the entire time interval selected for our analysis. Window length and filtering parameters are properly adjusted in order to detect similarities among the waveforms of different events in connection with each template event. Finally, the detected events are investigated in order to discriminate tectonic events from man-made events following specific criteria: working hours, working days, monthly distribution, magnitude and depth of the event correlation with specific templates. The catalogue resulted from this work is analysed compThe most important products of the seismological network are complete and reliable earthquake catalogs. Detecting earthquakes over an extended scale, from smallest magnitudes to large events is a critical issue in many studies, such as earthquake statistics, source seismology and seismic hazard. During the last years, the seismic network of Romanian has developed by increasing the number of stations and station coverage. Despite the significant improvement, the coverage is still not uniform all over the Romanian territory due to some natural limits (geographical borders, topography, etc.). Because of this, the monitoring and localization of local seismic events with low-magnitude using routine detection and localization methods is sometimes difficult and may lead to considerable magnitude or location errors. Recorded data affected by errors and quarry blasts recorded as seismic events (earthquakes) in the Romanian earthquake catalogue (ROMPLUS) will distort the seismicity pattern characterizing a specific region. The goal of this study is to increase the capability to detect and localize low-magnitude seismic events in the south-eastern part of Romania (Dobrogea region) by applying the cross-correlation method for 2012 – 2016-time interval. To this aim, we selected six templates for events recorded both during working hours and during night. The waveform similarity analysis was performed on signals recorded on the vertical component of the seismic station Targusor (TIRR), a high-quality station operating in the study region. The waveforms recorded for template events are cross-correlated with successive windows from the continuous waveform recording along the entire time interval selected for our analysis. Window length and filtering parameters are properly adjusted in order to detect similarities among the waveforms of different events in connection with each template event. Finally, the detected events are investigated in order to discriminate tectonic events from man-made events following specific criteria: working hours, working days, monthly distribution, magnitude and depth of the event correlation with specific templates. The catalogue resulted from this work is analysed comparatively with the existing routine catalogue for Dobrogea. aratively with the existing routine catalogue for Dobrogea.

Authors:
Mărmureanu G., Vacareanu R., Cioflan C.O., Ionescu C., Toma-Dănilă D.

Abstract:
The Vrancea seismogenic zone denotes a peculiar source of seismic hazard which represents a major concern in Europe, especially to Romania and neighbouring regions from Bulgaria, Serbia and Republic of Moldova. The strong seismic events that can occur in this area can generate the most destructive effects in Romania and may affect high-risk manmade structures such as nuclear power plants, chemical plants, large dams and pipelines located within a wide area including the Northern zone from the Republic of Bulgaria and the SW of the Moldavia Republic. A major part of the information for determining the design basis earthquakes consists of a complete set of historical earthquake data. Therefore, it is necessary that the available historical records to be collected, extending as far back in time as possible. Most of these historical records will be of descriptive nature, including such information as the number of houses damaged or destroyed, the behaviour of population etc. But from such information a measure of the intensity scale value of each earthquake in modern macroseismic intensity scale values may be determined. During the past project “Bridging the gap between seismology and earthquake engineering: from the seismicity of Romania towards a refined implementation of seismic action EN1998-1 in earthquake resistant design of buildings (BIGSEES)”, the authors developed the macroseismic intensity map of Romania by using newly compiled information about the damages experienced by 115 churches and monasteries after 10 strong earthquakes (Mw > 6.9) occurred in Vrancea zone starting with XVth century.

Authors:
Mihai A., Moldovan I-A., Toader V.E., Petrescu L, Partheniu R.

Abstract:
In this study were used geomagnetic data recorded during last 5 years, from 2013 till present. The records were corrected for missing and wrong data induced by malfunction of the data acquisition system. The main purpose of the paper is to identify the magnetic field behaviour in relation with space weather, meteorological phenomenon including annual/diurnal temperature variation, local and regional seismic activity. The paper is focusing on geomagnetic anomalies detected on the recorded field at one magnetometer located near Vrancea seismogenic zone prior to Mw>4.5 crustal and intermediate depth earthquakes. During these 5 years of investigations one crustal earthquake and three subcrustal earthquakes with a moment magnitude Mw between 5.0 and 6.0, occurred in the Vrancea zone. All three intermediate depth events were accompanied by significant anomalies on Y axis (EW component) of local geomagnetic field measured at MLR observatory. The MLR magnetometer was outside the preparation zone of the crustal earthquake, located at 100km distance from the epicenter, so no anomaly was observed. In order to highlight the anomalies recorded at Muntele Rosu (MLR) seismological observatory, these data were compared with data from Surlari (SUA) observatory, located about 150 Km South-East outside the Vrancea seismogenic zone. Similarly, earthquakes with Mw between 4.5 and 5 are accompanied by same type but smaller amplitude anomalies, were the drop on Y axis was less than 10 nT instead of 20-30 nT as those occurred prior to earthquakes with Mw>5.0. The latter ones are harder to observe during the summer time when these anomalies are hidden by large diurnal variations. The anomaly duration extends from days to sometimes months, without correlation with the earthquake magnitude. To better distinguish the local/regional anomalies from global geomagnetic behaviour, both MLR and SUA datasets were also corelated with the geomagnetic indices from NOAA/Space Prediction Center. The presence of geomagnetic storms creates a specific type of anomalies that sometimes might hide the ones related to earthquakes. The geomagnetic measurements were also compared with temperature values recorded at MLR station both for avoiding wrong interpretation of instrument response related to temperature variations, and to highlight possible correlations of magnetic field behaviour with ambient temperature. The three medium sized intermediate earthquakes that have occurred in the studied time interval provided a good opportunity to investigate the link between the presence of anomalies on geomagnetic records at Muntele Rosu observatory and seismicity in Vrancea zone.

Authors:
Moldovan I. A., Grecu B., Constantin A.P., Anghel A., Manea E.F., Manea L., Partheniu R.

Abstract:
In the last decade, many efforts were done to predict the macroseismic intensity in case of felt Vrancea earthquakes and additionally an online environment was developed for the automatic approximation of the intensity from peoples’ feedback. Besides the extended scientific studies, the near real-time estimation of the macroseismic intensity recently became mandatory for the insurance companies to cover some of the losses and damages that earthquakes might cause to houses, belongings, and other structures. Due to the insurance companies’ requests, the macroseismic questionnaires method was doubled by the seismic intensity determination using instrumental data, as recommended in the Romanian Seismic Intensity Scale Standard (STAS 3684-71). In the present study, the procedure is shown, for the last earthquakes with ML larger than 5.0, occurred in Vrancea zone, and felt on the extra-Carpathian area. We have selected the case study in Barlad, Vaslui county, because there have been recorded the largest accelerations (122 cm/s2) and have been reported the largest MSK intensities (VI) from Romania during the Mw 5.5 September 24, 2016 earthquake. The results obtained using the two approaches (macroseismic and instrumental data) have been compared and some differences have been found.

Authors:
Moldovan I.A., Manea L., Constantin A.P., Grecu B., Toma-Dănilă D.

Abstract:
Romania is one of the most seismic-prone countries in Europe due to the periodically occurrence of strong intermediate-depth earthquakes in Vrancea seismogenic zone. In the last decades, many efforts were done to gather macroseismic intensities in case of felt Vrancea earthquakes and additionally an online environment was developed for the automatic approximation of the intensity from people feedback. Besides the extended scientific studies, the near real time estimation of the macroseismic intensity recently became mandatory for the insurance companies to cover some of the losses and damage that earthquakes might cause to houses, belongings, and other buildings. The procedure proposed in this paper for rapid macroseismic estimation and loss assessment for the recent intermediate-depth Vrancea earthquakes with MW>4.5 is using the online macroseismic questionnaires, and the automatic intensity estimation code recently improved. Besides the automatic estimation, we have also used the classical approach to assess the intensity data points and also the available equations for conversion of peak ground acceleration in macroseismic intensity (including de Romanian Macroseismic Intensity Standard).

Authors:
Oros E., Moldovan I. A., Popa M., Diaconescu M., Ghiță C.

Abstract:
The paper presents a detailed analysis of the seismic activity recorded in the Banloc-Voiteg seismogenic structure (Romania) located on the southeastern border of the Pannonian Depression which is characterized by pre-Alpine and Alpine structures belonging to Tisa-Dacia Microplate and, particularly by the tectonic contact between two main geodynamic blocks. The seismic activity has a clear tendency to group on active neotectonic structures and displays different space and time patterns. Until now we have documented two major sequences (Imax=VIII EMS degree) in the study structure: October - November 1915 and July-December 1991. The 1991 sequence lasted several years, the seismic stations operated by NIEP recording thousands of aftershocks within several months. Some aftershocks had important macroseismic effects (e.g. 19.07.1991, Io=VII EMS). We refined hypocentral parameters for theis sequence using JHD relocation method. The new epicentres are well distributed in space and time defining two groups (phases) correlated with the faults systems in the study area. The focal mechanisms computed for the strongest events point out two orthogonal faults systems that were reactivated during the sequence, one oriented NE - SW (Banloc - Buzias Fault System) and the other one approximately E - W (Ittebej - Gataia Fault System) The seismic activity appears to migrate from South (Banloc phase, Mw=5.6, 12.07.1991) toward North (Voiteg phase, Mw=5.5, 02.12.1991) and further along Banloc - Buzias fault system.

Authors:
Ardeleanu L.

Abstract:
An inversion scheme using only few good quality high-frequency local waveforms was previously applied to estimate the source mechanism for a pilot set of crustal earthquakes with local magnitudes less than 4, from the bend of the South-eastern Carpathians. Taking advantage of the improved velocity and attenuation models recently determined for the study region, we reevaluate the focal mechanism of a couple of low-magnitude events (local magnitude ≥ 3), and assess the uncertainty of the fault plane solutions. The results evidence the increased reliability of the retrieved mechanisms and emphasize the capability of the approach to provide satisfactorily constrained fault plane solutions for the weak-to-moderate earthquakes in the study region.

Authors:
Ardeleanu L.

Abstract:
. We investigate the shear wave attenuation in the crust beneath the area from the bending of the Eastern Carpathians by using a procedure based on highfrequency waveform modelling. We determine 1-D local models of the quality factor of the medium Q, adequate for simulating the ground motion (waveforms with maximum frequency 5 Hz) generated by seismic sources of Vrancea region at locations within the extra-Carpathian zone. The results of the study reveal distinct attenuative properties among the structural units lying in the study region; considerably higher attenuation is evidenced beneath the Focşani Basin and the Vrancea region orogen.

Authors:
Bala A., Tătaru D., Grecu B.

Abstract:
Tectonic of Romania includes both pre-alpine platforms and Alpine orogenic structures. The pre-alpine platforms are: Eastern European Platform, with its western margin in Romania—Moldavian platform; Scythian platform; Moesian platform.

Authors:
Chalyi O., Diaconescu M., Gurova I., Lisovyi Y., Pigylevsky P., Shcherbina S., Shevtsov A., Shumlianska L.

Abstract:

Authors:
Cioflan C.O., Radulian M., Ionescu C. Bălan S.F., Apostol B.F.

Abstract:
The paper's goal is to discuss some aspects regarding the influence of the dominant periods of the soil layers and fundamental periods of the built structure, starting from earthquakes records and using already known data about the oscillation period of the subsoil. We will focus our analysis on Bucharest Metropolis foundation soils, where buildings are placed in an area exposed to high seismic hazard. The regions of the south-east and south of Romania are affected mainly by the Vrancea strong earthquakes, generated at the South-Eastern Carpathians Arc bend at intermediate depth. In the XXth century four major earthquakes (Mw > 7) were reported. The methods used for computing the oscillation period of the soil are reviewed. By knowing the dominant periods over the Bucharest area, we can appreciate if a building is suitable or not for a specific site. In the authors’ opinion, it is safer to pick the right structure to be build up in a given area than to force a non-resonance design in that place. Consequently, some seismic risk considerations from soil-foundation-structure interaction perspective will be presented. This will have to be a very effective way of getting the right answers when trying to build a special construction on a site.

Authors:
Oros E., Plăcintă A. O., Popa M.

Abstract:
Intra-Carpathian Region of Romania experienced strong earthquakes as it is mentioned in the national and international databases, e.g. November 26, 1829 (Ms = 6.4), October 10, 1834 (Ms = 6.3), January 26, 1916 (Ms = 6.4), July 12, 1991 (Mw = 5.7). The paper focuses on calibration and validation of MEEP method (Macroseismic Estimation of Earthquake Parameters, Musson & Jimenez, 2008) to provide a homogeneous and repeatable procedure for processing intensity data points (IDPs) which may supply the location and magnitude Mw of historical earthquakes occurred in the Intra-Carpathian Region of Romania and surroundings. The MEEP method is based on 1) grid-search technique for locating the epicentres and 2) the felt area approach to estimate the magnitude. It has the advantage to be used for small and moderate events. We used two high-quality datasets of earthquakes of the 20th century for which macroseismic data points (IDPs), instrumental moment magnitude (Mw) and instrumental epicentral coordinates are available, one for calibration and the other one for validation of the method. The main parameters used through MEEP algorithm were calibrated at regional scale using high-quality instrumental data: 1) crustal attenuation Q3 = 435 (Q at f = 3 Hz, which is understood to be the limit of the human perception of seismic waves), 2) Kövesligethy's inelastic attenuation (∝ = 0.0065), 3) isoseismic spacing coefficient (k = 3.1) and 4) C = 2015, a constant generally related to tectonic regime. The MEEP method was successfully tested for events occurred within extra-Carpathian regions and the Pannonian Basin.

Authors:
Craiu A., Ghiță C., Craiu M., Diaconescu M., Mihai M., Ardeleanu L.

Abstract:
The moderate-size earthquake (local magnitude 5.7) which occurred on November 22, 2014 in Vrancea region (Romania), is the largest crustal event instrumentally recorded. Its aftershock sequence lasted around 70 days, 222 earthquakes with local magnitude ≥ 0.1 being located using the records collected by the Romanian seismic network. The seismic sequence occurred mainly in the lower crust (depths greater than 25 km), and the epicenter distribution – along a NNE-SSW direction followed the orientation of the Vrancea crustal earthquakes alignment. The sequence, occurred in the Focsani Basin (part of the Moesian Platform) and is related to the normal fault system associated to the major Peceneaga - Camena fault, which separates the Moesian Platform from the North Dobrogea promontory. The spatio-temporal distribution of the seismic activity, as well as the seismic energy released during the seismic sequence are analysed in detail, and the focal mechanisms of the largest events – 34 shocks with ML ≥ 1.8 – are determined using reliable P-wave polarities and amplitude ratios. Taking into consideration that the moderate-size shock of November 22, 2014 is the strongest instrumentally recorded crustal earthquake in the region, its focal mechanism provides highly relevant seismological information on the deformation field in front of the Carpathian bend. The obtained fault plane solution indicates normal faulting with a dominant dip-slip component; both nodal planes being oriented NW-SE.

Authors:
Grecu B., Neagoe C., Tătaru D., Zaharia B., Borleanu F.

Abstract:
We present the first detailed investigation of the background seismic noise recorded in the Romanian-Bulgarian cross-border region over 3 years (2012–2015). We used the power spectral densities probability density functions (PSD PDFs) to study the noise variations in the period domain (0.025–1 s) as well as in the secondary microseism band (2–10 s). Strong diurnal variations and an increase of the noise levels during working days were observed at high frequencies at all stations, thus confirming the anthropic origin of the noise at low periods. The noise variations observed at longer periods (> 1 s) are relatively small among the stations and are related to season changes. The dominant feature in the noise spectra between 2 and 10 s is the double-frequency peak (DFP) whose amplitude increases and changes during winter. For a specific interval, from 25th to 27th of January 2014, when a storm was reported in the Black Sea area, the maximum of the DFP shifted from larger periods (~ 5.5 s) at stations far from the Black Sea towards smaller periods (~ 1.8 s) at stations located on the coastline. The polarization analysis showed that the short period double-frequency microseisms originating from the Black Sea dominate during the winter month. Finally, we showed that site conditions vary due to noise variations related to weather conditions in the Black Sea or to changes in anthropogenic noise sources.

Authors:
Grecu B., Zaharia B., Diaconescu M., Bala A., Nastase E., Constantinescu E., Tătaru D.

Abstract:
Strong motion data are essential for seismic hazard assessment. To correctly understand and use this kind of data is necessary to have a good knowledge of local site conditions. Romania has one of the largest strong motion networks in Europe with 134 real-time stations. In this work, we aim to do a comprehensive site characterization for eight of these stations located in the eastern part of Romania. We make use of a various seismological dataset and we perform ambient noise and earthquake-based investigations to estimate the background noise level, the resonance frequencies and amplification of each site. We also derive the Vs30 parameter from the surface shear-wave velocity profiles obtained through the inversion of the Rayleigh waves recorded in active seismic measurements. Our analyses indicate similar results for seven stations: high noise levels for frequencies larger than 1 Hz, well defined fundamental resonance at low frequencies (0.15–0.29 Hz), moderate amplification levels (up to 4 units) for frequencies between 0.15 and 5–7 Hz and same soil class (type C) according to the estimated Vs30 and Eurocode 8. In contrast, the eighth station for which the soil class is evaluated of type B exhibits a very good noise level for a wide range of frequencies (0.01–20 Hz), a broader fundamental resonance at high frequencies (~ 8 Hz) and a flat amplification curve between 0.1 and 3–4 Hz.

Authors:
Guéguen P., Țigănescu A.

Abstract:
The real-time analysis of a structure’s integrity associated with a process to estimate damage levels improves the safety of people and assets and reduces the economic losses associated with interrupted production or operation of the structure. The appearance of damage in a building changes its dynamic response (frequency, damping, and/or modal shape), and one of the most effective methods for the continuous assessment of integrity is based on the use of ambient vibrations. However, although resonance frequency can be used as an indicator of change, misinterpretation is possible since frequency is affected not only by the occurrence of damage but also by certain operating conditions and particularly certain atmospheric conditions. In this study, after analyzing the correlation of resonance frequency values with temperature for one building, we use the data mining method called “association rule learning” (ARL) to predict future frequencies according to temperature measurements. We then propose an anomaly interpretation strategy using the “traffic light” method.

Authors:
Pilger C., Ceranna L., Ross J.O., Vergoz, J., Le Pichon A., Brachet N., Blanc E., Kero J., Liszka L., Gibbons S., Kvaerna T., Näsholm S. P., Smets P., Evers L., Marchetti E., Ripepe M., Sindelarova T., Lastovicka L., Ghica D., Ionescu C., Ben Horin Y., Mialle P.

Abstract:
The European Infrasound Bulletin highlights infrasound activity produced mostly by anthropogenic sources, recorded all over Europe and collected in the course of the ARISE and ARISE2 projects (Atmospheric dynamics Research InfraStructure in Europe). Data includes high-frequency (> 0.7 Hz) infrasound detections at 24 European infrasound arrays from nine different national institutions complemented with infrasound stations of the International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Data were acquired during 16 years of operation (from 2000 to 2015) and processed to identify and locate ∼ 48,000 infrasound events within Europe. The source locations of these events were derived by combining at least two corresponding station detections per event. Comparisons with ground-truth sources, e.g., Scandinavian mining activity, are provided as well as comparisons with the CTBT Late Event Bulletin (LEB). Relocation is performed using ray-tracing methods to estimate celerity and back-azimuth corrections for source location based on meteorological wind and temperature values for each event derived from European Centre for Medium-range Weather Forecast (ECMWF) data. This study focuses on the analysis of repeating, man-made infrasound events (e.g., mining blasts and supersonic flights) and on the seasonal, weekly and diurnal variation of the infrasonic activity of sources in Europe. Drawing comparisons to previous studies shows that improvements in terms of detection, association and location are made within this study due to increasing the station density and thus the number of events and determined source regions. This improves the capability of the infrasound station network in Europe to more comprehensively estimate the activity of anthropogenic infrasound sources in Europe.

Authors:
Popa, M., Munteanu I., Borleanu F., Oros E., Radulian M., Dinu C.

Abstract:
Active tectonic deformation is continuously shaping the landscape in the Alpine Orogenic system. Earthquakes are clear proves of neotectonic deformation process. In the Romanian Carpathians the most active deformation is recorded in the South Eastern Carpathian Bend Zone. Nevertheless, seismicity associated to latest orogenic stage of active deformation is not limited to this area. Other seismic regions, like the South West Carpathians Bend Zone, were identified. Recently, several earthquake sequences were recorded in the Caransebes-Mehadia (CMB) and Hateg basins (HB). These sedimentary basins developed over the South Carpathians, Getic/Supra Getic and Danubian basement napes, their evolution being related with the N-ward tectonic transport of the Carpathian Orogen, in the current position, during the Paleogene-Quaternary times. The aim of the present study is to perform a thorough analysis of the earthquakes recorded in these two basins in correlation with the observed geological structure to better understand and constrain the neotectonic processes affecting the SW Carpathians Bend Zone. The focal mechanisms determined for HB show a predominant strike-slip faulting component with the principal axes oriented approximately NW–SE (compression) and NE–SW (extension), a reorientation from the N-S one described for the Pliocene–Pleistocene phase. The focal mechanisms in CMB imply N–S extension with normal or strike-slip faulting. We argue that the present day tectonic processes are not restricted to the SE Carpathians Bend zone, as previously inferred. Instead they affect a much larger area of the Carpathian Orogen, like the SW Carpathians Bend zone.

Authors:
Popescu E., Radulian M., Bala A., Toma-Dănilă D.

Abstract:
Earthquake mechanism information is fundamental to determine the stress field and to define seismogenic zones. At the same time, it is a basic input to compute seismic hazard by deterministic approach. The present paper extends the catalogue of the fault plane solutions for the earthquakes in Romania, previously completed until 1997, for 1998-2012 time interval. The catalogue is limited geographically to the Carpathians Orogeny and extra-Carpathians area located in the southeastern part of Romania because similar investigations cover the rest of the country. The catalogue comprises 259 intermediate-depth seismic events and 90 crustal seismic events, recorded in the considered time interval with acceptably constrained fault plane solutions. We use specific graphical tools in order to emphasize statistically representative features of the stress field as coming out from our results. The fault plane solutions of the Vrancea earthquakes generated in a confined sinking plate in the mantle reflect the dominant geodynamic process in the study region. The typical features revealed by all the previous studies on the subcrustal seismic activity (predominant dip-slip, reverse faulting, characterizing both the weak and strong earthquakes) are reproduced as well by our investigation. As concerns the earthquake activity in the crust, a few new refined aspects are highlighted in the present work: (1) a deficit of the strike-slip component over the entire Carpathians foredeep area, (2) different stress field pattern in the Făgăraş-Câmpulung zone as compared with the Moesian Platform and Pre-Dobrogean and Bârlad Depressions, (3) a larger range for the dip angle of the nodal planes in the Vrancea subcrustal source, ~ 40 0-70 0 against ~ 70 0 , as commonly considered.

Authors:
Popova O., Rybnov Y., Kharlamov V., Ghica D., Borovicka J.

Abstract:

Authors:
Radulian M., Bala A., Popescu E., Toma-Dănila D.

Abstract:
Earthquake mechanism information is fundamental to determine the stress field and to define seismogenic zones. At the same time, it is a basic input to compute seismic hazard by deterministic approach. The present paper extends the catalogue of the fault plane solutions for the earthquakes in Romania, previously completed until 1997, for 1998 – 2012 time interval. The catalogue is limited geographically to the Carpathians Orogeny and extra-Carpathians area located in the south-eastern part of Romania because similar investigations cover the rest of the country. The catalogue comprises 259 intermediate-depth seismic events and 90 crustal seismic events, recorded in the considered time interval with acceptably constrained fault plane solutions. We use specific graphical tools in order to emphasize statistically representative features of the stress field as coming out from our results. The fault plane solutions of the Vrancea earthquakes generated in a confined sinking plate in the mantle reflect the dominant geodynamic process in the study region. The typical features revealed by all the previous studies on the subcrustal seismic activity (predominant dip-slip, reverse faulting, characterizing both the weak and strong earthquakes) are reproduced as well by our investigation. As concerns the earthquake activity in the crust, a few new refined aspects are highlighted in the present work: (1) a deficit of the strike-slip component over the entire Carpathians foredeep area, (2) different stress field pattern in the Făgăraş – Câmpulung zone as compared with the Moesian Platform and Pre-Dobrogean and Bârlad Depressions, (3) a larger range for the dip angle of the nodal planes in the Vrancea subcrustal source, ~ 400 -700 against ~ 700, as commonly considered.

Authors:
Oros E., Popa M., Diaconescu M

Abstract:
The study region is the most important seismic region of Romania when we refer to the crustal seismicity as a source of seismic hazard. So far there have been recorded 91 seismic events that produced significant effect in buildings (Io ≥ 6 EMS), some of them resulting in severe damage and even casualties (Io ≥ 7 EMS). In this paper we modelled the seismogenic sources in the region using a new seismotectonic model constructed on new earthquakes and focal mechanisms catalogues basis. This model was elaborated starting from the relationship between geology and historical and instrumental seismicity and then it was better constrained by geophysical, neotectonic, geodetic data and particularly by active stress field features. The stress tensor parameters and the stress regime have been determined by formal inversion of the focal mechanisms solutions. Our study provides evidence of at least seven different deformation domains with different tectonic regimes as a realistic support for assessing the seismogenic potential of the geological structures. Each seismogenic source is characterized by completeness magnitude (Mcomp), maximum probable magnitude (Mmax) and magnitude—recurrence parameters. The probabilistic hazard maps produced in terms of PGA using the new seismic sources highlights the importance of their configuration on the hazard parameter values and their spatial distribution.

Authors:
Toma-Danila D.

Abstract:
Through this paper we propose and test a GIS framework that addresses the issue of seismic risk due to urban road network failure. The approach relies on full GIS integration, on Monte Carlo simulations for generating potentially disrupted network configurations, considering also the damage probability due to direct earthquake implications, and on traffic considerations (both in typical and post-earthquake situations). The damage probability can be obtained using fragility functions for critical structures like bridges and tunnels or by determining empirically the possibility of affected buildings to generate debris leading to road obstruction. Multiple performance indicators such as travel time and distance under various conditions are combined, in order to quantify the risks inflicted by dysfunctionalities in the emergency intervention process. The framework considers at the same time temporal and spatial dimensions, being able to cope with traffic dynamics or reconfigurable network configurations. The ArcGIS Network Analyst Module is used for model integration, and full city scale analysis is performed in order to test the capabilities. Bucharest (capital of Romania) is selected for the case study; this 2 million inhabitant city is one of the most endangered in Europe, due to earthquakes that occur in the Vrancea Area, at intermediate depth, with moment magnitudes > 7, but also due to the vulnerable building stock. Beside this, it is one of Europe’s top cities when it comes to traffic congestion. The results of the study provide initial insights on the deficiencies of the city’s road network and connectivity limitations, showing the high impact of road obstructions and traffic congestion on intervention times, for ambulances and firefighters, in case of an earthquake.

Authors:
Zoran M.A., Savastru R.S., Savastru D.M., Mateciuc D.N.

Abstract:
Earthquake science has entered a new era with the development of space-based technologies to measure surface geophysical parameters and deformation at the boundaries of tectonic plates and large faults. Satellite time-series data, coupled with ground based observations where available, can enable scientists to survey pre-earthquake signals in the areas of strong tectonic activity. Cumulative stress energy in seismic active regions under operating tectonic force manifests various earthquakes’ precursors. Space-time anomalies of Earth’s emitted radiation (thermal infrared in spectral range measured from satellite months to weeks before the occurrence of earthquakes, radon in underground water and soil, etc.), and electromagnetic anomalies are considered as pre-seismic signals. This paper presents observations made using time series MODIS Terra/Aqua and NOAA-AVHRR satellite data for derived multi-parameters land surface temperature (LST), outgoing long-wave radiation (OLR), net surface latent heat flux (LHF), mean air temperature (AT), Relative Humidity (RH), and reanalysis data sets for some moderate or strong seismic events recorded in Vrancea region in Romania, which is one of the most active intracontinental seismic areas in Europe. Starting with almost one week prior to a moderate or strong earthquake a transient thermal infrared rise in LST of several Celsius degrees (oC) and the increased OLR values higher than the normal have been recorded around epicentral areas, function of the magnitude and focal depth, which disappeared after the main shock. These observations support seismic LSAIC (Lithosphere – Surfacesphere – Atmosphere -Ionosphere Coupling) Model.

Authors:
Constantin A.P., Partheniu R., Moldovan I.A., Pantea A.

Abstract:
On April 25, 2009, at 20:18:48 (local hour) the Romanian territory was shaken by a moderate size earthquake centred beneath the bending area of the southeastern Carpathians, in the Vrancea seismogenic region (Romania). In the present paper we present intensity map, macroseismic intensities, and community observations of effects for the M-W = 5.4 Vrancea subcrustal earthquake of 25 April, 2009. For many locations, for the estimation of the macroseismic intensities besides questionnaires other type of sources such as press reports, internet were used. The highest intensity assigned for this Vrancea earthquake was VI MSK, estimated for eleven locations, situated in the north-eastern part of Vrancea seismogenic zone, which include parts from Vrancea, Bacau, and Galati counties. At the lowest intensities, the 2009 earthquake was felt to a distance of 500 km from the epicenter, in Rep. of Moldova, Bulgaria, Ukraine, and Serbia. A non-uniform distribution of intensity resulted for locations on different directions from the epicenter. A scatter of as much as one-two intensity units were observed for places situated very close. The comparison of the intensity areas for the October 27, 2004 and April 25, 2009 moderate subcrustal earthquakes of the Vrancea seismogenic zone was performed.

Authors:
Poiată N., Miyake H.

Abstract:
We estimated the parameters of strong motion generation areas and simulated broadband ground motions for the moderate October 27, 2004 (M-w 5.8) and damaging March 4, 1977 (M-w 7.4) Vrancea (Romania) intermediate-depth subduction earthquakes using the empirical Green's function method. The method allows the simulation of ground motions in a broadband frequency range by summing up the subevent records, corresponding to small magnitude events in the near-source areas, which are assumed to follow the source-scaling relationship and the omega-square source spectral model. We first estimated the strong motion generation area that reproduces near-source ground motions in a broadband frequency range of 0.3-10 Hz for the 2004 earthquake, by fitting the synthetic acceleration, velocity, and displacement waveforms to the observed data. The source properties of the obtained strong motion generation area are in agreement with the predictions made using an empirical source scaling relationship for crustal earthquakes, implying a stress drop of approximately 10 MPa for the 2004 earthquake. We then modeled the strong motion generation area for the 1977 damaging earthquake using the 2004 earthquake as an empirical Green's function and constructing a source model based on its estimated source parameters. To simulate the unique record at Bucharest, capital city of Romania, the rupture was assumed to have propagated from the northeast bottom of the strong motion generation area having a stress drop of 50 MPa. Broadband ground motion simulations were further compared in terms of the modified Mercalli intensity values, calculated from the peak ground accelerations and peak ground velocities of synthetic waveforms, with the observed Medvedev-Sponheuer-Karnik intensity values. Our estimates of the source properties for the 2004 and 1977 Vrancea intermediate-depth earthquakes support the size-dependent stress drop.

Authors:
Poiată N., Miyake H., Koketsu K.

Abstract:
We analyzed the seismological aspects of the near-fault ground motion pulses and studied the main characteristics of the rupture configuration that contribute to the pulse generation for dip-slip faulting events by performing forward simulations in broadband and low-frequency ranges for different rupture scenarios of the 2009 L'Aquila, Italy (M-w 6.3) earthquake. The rupture scenarios were based on the broadband source model determined by Poiata et al. (Geophys J Int 191:224-242, 2012). Our analyses demonstrated that ground motion pulses affect spectral characteristics of the observed ground motions at longer periods, generating significantly larger seismic demands on the structures than ordinary records. The results of the rupture scenario simulations revealed the rupture directivity effect, the radial rupture propagation toward the site, and the focusing effect as the main mechanisms of the near-fault ground motion pulse generation. The predominance of one of these mechanisms depends on the location of the site relative to the causative fault plane. The analysis also provides the main candidate mechanisms for the worst-case rupture scenarios of pulse generation for the city of L'Aquila and, more generally, the hanging-wall sites located above the area of large slip (strong motion generation area).

Authors:
Toma-Dănilă D., Cioflan C., Ionescu C., Țigănescu A.

Abstract:
Romania is one of Europe's countries with the greatest seismic hazard, mainly due to major earthquakes originating in the subcrustal Vrancea Source. A future major earthquake could be a shock, therefore it is vital to estimate in actual context the size and distribution of losses, based on scenarios (leading to seismic mitigation), but also in real-time (with impact on effective emergency response). Since 2011, the National Institute for Earth Physics engaged in this effort and created SeisDaRo-a system dedicated to the estimation of seismic damage in Romania, in terms of building damage and fatalities. In 2016, a 3 rd version, described in this paper, was released, providing significant upgrades: a custom ShakeMap module for computing faster and more representative to Vrancea Source intensities and accelerations, and a module representing an adaptation to Romania of the USGS's PAGER methodology. The other version's module relying on the SELENA software is also included, using the Improved Displacement Coefficient Method for estimating building failure probability and HAZUS method for fatality estimation. As building and population database, SeisDaRo now uses newer data from the 2011 National Census. The system is functional in real-time, collecting input now also from the NIEP's Early Warning System; therefore, SeisDaRo 3 can generate a range for fatality estimates within 35 seconds after the alarm is issued. All modules provide results in less than 6 minutes. In order to test the system, we used 5 relevant Vrancea earthquake scenarios (with magnitudes from 6.4 to 7.7). Results show that although estimations using the two different modules do not match exactly (SELENA apparently slightly overestimates), representative insights regarding the potential damage scale of Vrancea earthquakes can be extracted.

Authors:
Toma-Dănilă D., Cioflan C., Manea E.F.

Abstract:
In the context of an ever-increasing exposure, the estimation of direct and indirect earthquake impact is vital to building resilient societies. As recent events showed, road networks are an essential support for rapid intervention and long-term recovery, but they can also be severely affected by seismic and seismically-triggered events, leading to additional risks. In order to aid in mitigation efforts, we investigate the potential impact of strong earthquakes on the Romanian national road network. The methodology implies combining in GIS multiple layers regarding road network characteristics, seismic hazard, landslide susceptibility and road damage index obtained based on previous earthquake experiences, in order to generate a relative estimation of the most critical road segments. This estimation contributes to the determination of potentially affected/isolated areas and to an assessment of the number of road kilometers with failure capacity. Although the data used is limited (vector road network data is obtained from OpenStreetMap since official GIS data is non-existent, no considerations for road structures like bridges could be made), the analysis reveals general aspects with contribution in revealing general damage patterns and indicating areas to be analyzes more in detail. The framework can easily be adapted to other study areas. Results reveal the influence of intermediate-depth Vrancea earthquakes, which have the potential of generating a vast amount of damage over a wide-extent area.

Authors:
Bălă A., Radulian M., Popescu E., Toma-Dănilă D.

Abstract:
Earthquake mechanism and fault plane solution information is fundamental to determine the stress field and to define seismogenic and active tectonic zones. At the same time, it is a basic input to compute seismic hazard by deterministic approach. The purpose of this paper is to update the catalogue of the fault plane solutions for Romanian earthquakes for the time interval 1998–2012. The catalogue is limited geographically to the Carpathians Orogeny and extra-Carpathians area located in the south—eastern part of Romania. The catalogue comprises 259 intermediate-depth seismic events and 90 crustal seismic events, covering the study time interval. All the existing information is considered and revised. The fault plane solutions of the Vrancea earthquakes generated in a confined sinking plate in the mantle reflect the dominant geodynamic process in the study region. The typical features revealed by all the previous studies on the subcrustal seismic activity (predominant dip-slip, reverse faulting, characterizing both the weak and strong earthquakes) are reproduced as well by our investigation. As concerns the earthquake activity in the crust, a few new refined aspects are highlighted in the present work: (1) a deficit of the strike-slip component over the entire Carpathians foredeep area, (2) different stress field pattern in the Făgăraş—Câmpulung zone as compared with the Moesian Platform and Pre-Dobrogean and Bârlad Depressions, (3) a larger range for the dip angle of the nodal planes in the Vrancea subcrustal source, ~400–700 against ~700, as commonly considered.

Authors:
Bălan S.F., Țigănescu A., Apostol B.F

Abstract:
The paper presents accelerations, response spectra and spectral ratio for two tower-type buildings, one in Southern part of Bucharest, T1, at 160 km from the epicenter zone, and other, T2, near the epicenter zone, Vrancea. These seismic characteristics are all from recorded earthquakes triggered in the above mentioned area. 3 triaxial seismic accelerometers were used on 3 levels at each building. The accelerations recorded on the analyzed structures were a result of Vrancea medium magnitude earthquakes between 2014-2017 years, with magnitudes Mw ranging from 3.8 to 5.6, and focal depths between about 40 km to 148 km. An analysis of structural response was made concerning each building, T1 on 12 seismic events and T2 on 6 ones, and with 4 common seismic events for both structures. Maximum accelerations at three buildings levels and acceleration response spectra at the basement of buildings are calculated for two strongest earthquakes, and spectral ratio (top/base) for three, respectively two strongest seisms. The recorded data and subsequent analysis will contribute to a better understanding of the structures responses, even subjected to medium magnitude seismic events, and to the mitigation of seismic risk for densely populated areas.

Authors:
Constantin A.P., Moldovan I. A., Partheniu R.

Abstract:
The goal of this paper is to present some observations about the abnormal animal behavior prior to and during some Romanian subcrustal earthquakes. The major Vrancea earthquakes of 4 March 1977 (MW = 7.4, Imax = IX–X MSK), 30 August 1986 (MW = 7.1, I0 = VIII–IX MSK) and 30 May 1990 (MW = 6.9, I0 = VIII MSK), were preceded by extensive occurrences of anomalous animal behavior. These data were collected immediately after the earthquakes from the affected areas. Some species of animals became excited, nervous and panicked before and during the earthquakes, such as: dogs (barking, howling and running in panic), cats, birds (hens, geese, turkey hens, ducks, pigeons, parrots), cattle, pigs, mice and rats (came into the houses and have lost their fear), horses, fishes, snakes etc. These strange manifestations of the animals were observed on the entire territory of the country, especially in the extra-Carpathian area. This unusual behavior was noticed within a few seconds to days before the seismic events, but for the most of cases the time of occurrence was within two hours prior to the quakes. We hope that one day the abnormal animal behavior will be documented enough in order to be used as a reliable seismic precursor for the intermediate depth earthquakes.

Authors:
Tătaru D., Toma-Dănilă D., Grecu B., Năstase E.

Abstract:
Research institutions and academia play an important role in developing new methods for disaster management and advancing the state-of-the art in risk reduction. In the case of natural disaster studies, fundamental research and theoretical approaches can be directed toward the development of new tools and technologies with direct applicability in the management of emergency situations and in risk mitigation. What needs to be considered by all those actors who can contribute to strengthening the response capacity and raising the level of information of decision-makers, intervention units and society is precisely the adjustment of the tools developed for the purpose in which they will be used. The information required by decision makers covers a wide range of spatial and temporal scales and more important, needs to be timely delivered, continuously updated, easily accessible and understandable. This becomes a challenge in itself, considering that the information will come at the end of the processing flow and at different stages of scientific analysis and interpretation. In this paper, we underline the best practices implemented in Romania, a country with a high seismic risk, through a scientific investigation focused on the results of seismic monitoring hazard assessment and active collaboration among institutions involved in natural hazards risk management. Going from GIS mapping tools to early warning system and then to dedicated communication, training and education facilities, the support instruments are discussed in terms of advantages and limitations. We also address the importance of communication among scientists, disaster managers and community planners as well as public outreach to assure that everybody knows what tools are available and what issues can be addressed.

Authors:
Tătaru D., Toma-Dănilă D., Năstase E.

Abstract:
Over the last few years, science has advanced unprecedentedly in explaining phenomena and facts with a high impact on society: earthquakes for example. On the other hand, new technologies are transforming the way (seismological) information is collected and transmitted to public and other various stakeholders categories. From interactive multimedia content to immersive experiences, difficult concepts become easier to be transmitted and understood by a wide variety of audience, starting with children, a most important part of tomorrow?s society. But what if the aiming is far more than captivating young people or promoting science and scientific results? How can we, scientists, deliver information in such a way that awareness and mitigation comes immediately after or even together with learning and understanding? For a quake-prone country, earthquakes have to be a major and continuous concern, but depending on the recurrence period of damaging events, effective measures for mitigation might not be disregarded but considered as top priority. Romania is a good example, with an average of 2-3 earthquakes with magnitude greater than 7 per century. Although the seismic hazard was recently reevaluated and ranked one in the top of hazards with the greatest impact on population and economy, and also giving that questionnaires indicated that people are most afraid of earthquakes, the preparedness actions are very slow in Romania. One of the reasons lie in the fact that people forgot what an earthquake can do (as they also did prior to the 1940 and 1977 events). That is why special tools are necessary to address the needs for education and awareness in a technologically oriented society. In a world where information delivered through social media travels much faster than seismic waves, scientists need to adapt and be more present as an authoritative and relevant source of information. In this context, a partnership that brings together the unique expertise of geoscientists, visual designers and digital content developers was established, in order to develop and deliver a modern and innovative product: a Mobile Earthquake Exhibition (MOBEE). MOBEE aims to mobilize wide public as well as media and decision makers to increase earthquake preparedness by delivering and wisely spreading earthquake information and scientific explanations related to this natural hazard. The exposition makes use of new digital technologies (mobile apps, mapping tools or touch screen devices) but also explores the interplay between science and art, or more precisely how visual art can help better explain and transmit science concepts and generate new research and visual communication tools about seismic safety.

Authors:
Tătaru D., Poiată N., Grecu B.

Abstract:

Authors:
Alcik H., Mărmureanu A., Toader V.E., Ionescu C, Zulfikar C.

Abstract:
Natural disasters from earthquakes can cause considerable damage, with potentially severe effects to urban environment. The last strong Vrancea earthquake was on March 4, 1977 (Mw=7.4, depth=95km); tens of thousands of buildings damaged, many people injured and dead. Strong earthquakes in the Vrancea zone occur between 60-200 km depth within an almost vertical column. Bucharest Earthquake Early Warning (EEW) system detects earthquakes with a seismic network in the epicentral Vrancea region and issues a warning in Bucharest providing 20-25s warning time. In this study, we have investigated the relationships of the bracketed cumulative absolute velocity window (BCAV-W) approach versus epicentral distance and magnitude for Vrancea region. Firstly, a set of time histories contains 11 earthquakes, 111 strong ground motion records for intermediate depth earthquakes with different magnitudes (4.0≤Mw≤6.0) and epicentral distances (0-200 km) are analyzed to determine relations between the window size (W) and BCAV-W ratio. The BCAV-W computed for different windows time size 2s, 4s, 8s, 12s, 16s, 32s, 64s, 128s and 256s have the ratios 24%, 40%, 61%, 74%, 84%, 97%, 97%, 100% and 100% to the total BCAV respectively. The results show that there is no significant benefit to choose a window size more than 16s. Subsequently, rational threshold levels related to Mw=5.4+ earthquakes are determined as 0.28 m/s and 0.34 m/s related to 12-second and 16-second windows, respectively. The goal of the paper is to enhance EEW capability to decrease the effects of Vrancea earthquakes on urban and built environment.

Authors:
Apostol B. F.

Abstract:
The elastic displacement in an isotropic elastic half-space with free surface is calculated for a point tensor force which may arise from the seismic moment of seismic sources concentrated at an inner point of the half-space. The starting point of the calculation is the decomposition of the displacement by means of the Helmholtz potentials and a simplified version of the Grodskii-Neuber-Papkovitch procedure. The calculations are carried out by using generalized Poisson equations and in-plane Fourier transforms, which are convenient for treating boundary conditions. As a general result we compute the displacement in the isotropic elastic half-space with free surface caused by point forces with arbitrary structure and orientation, localized either beneath the surface (generalized Mindlin problem) or on the surface (generalized Boussinesq-Cerruti problems). The inverse Fourier transforms are carried out by means of Sommerfeld-type integrals. For forces buried in the half-space explicit results are given for the surface displacement, which may exhibit finite values at the origin, or at distances on the surface of the order of the depth of the source. The problem presented here may be viewed as an addition to the well-known static problems of elastic equilibrium of a half-space under the action of concentrated loads. The application of the method to similar problems and another approach to the starting point of the general solution are discussed.

Authors:
Apostol B. F.

Abstract:
The motion a point harmonic oscillator coupled to a homogeneous elastic medium and localized either on the medium’s surface or embedded in the medium is analzyed. Two new elements are introduced, one regarding the reaction of the oscillator upon the medium and another concerning a coupling function. The present analysis is meant to be relevant for the effects a seismic motion may have upon a localized structure, either natural or man-built. It is shown that the reaction of the oscillator modifies its inertia, which in turn leads to a change in the oscillator’s eigenfrequency; this change is controlled by the coupling function. The present treatment opens the way of introducing new, more realistic features in analyzing the effect of the seismic motion upon localized structures, in particular the non-linear features of the coupling of the structure with its local site’s motion.

Authors:
Moldovan I.A., Toader V.E., Moldovan A.S., Ghica D., Constantin A.P.

Abstract:
he atmospheric sound waves with frequencies lower than 20Hz are named infrasound waves. Among the multitude of infrasonic signals that have been recorded and detected during time, some of them have been associated with different natural or anthropogenic sources and the source of many other remaining hidden and unknown. At the beginning of year 2013, a permanent infrasound monitoring system composed by a MB AZEL2007 microbarometer, the digitizer and the transmitting equipment, was installed by NIEP, at Mangalia, Romania, on the Black Sea coast line (at 50m from the water front) to test the infrasonic method in correlation with local, regional, and global sources producing acoustic waves with frequencies lower than 20Hz. Five years of recordings show at lower frequencies (less than 2Hz) a predictable behavior of infrasonic activity on the seashore, suggesting the presence of highly coherent infrasound waves in atmosphere. At higher frequencies (2Hz-8Hz) there appeared a type of waves that was never recorded before by our infrasonic sensors in other locations far away from the sea shore. The interesting aspect on the spectrogram resides in well defined, visible superior harmonics of the dominant signal, which develops between 2 and 8Hz. These harmonics are clear and create the specific spider legs aspect present in spectrograms. The precise source of these high amplitude signals at higher frequencies is under investigation and a couple of suppositions have been made. One of them refers to the composition of atmosphere that might be possible to act as a band pass filter which selects certain preferred frequencies from the background infrasonic noise induced by water's surface. The propagation parameters of this filter may be altered by aerosols concentration, humidity, temperature and, perhaps, by other factors. The corroboration of the infrasound recordings and spectrograms with local meteorological data show a good correlation between the spectrogram and the daily variation of the humidity parameter.

Authors:
Apostol B. F.

Abstract:
The notions of ‘elementary’ seismic sources and ‘elementary’ earthquakes are introduced, as being associated with ‘elementary’ tensorial point forces with a -like time dependence (where is the Dirac delta function). The tensorial character of these forces, known in Seismology as the dipole (or double-couple) representation, is given by the tensor of the seismic moment. A regular seismic source and a regular earthquake can be represented as a superposition of elementary sources and, respectively, elementary earthquakes, governed by a space-time structure factor of the seismic focal region. All these are new concepts. Elementary seismic sources are considered here for a homogeneous isotropic elastic half-space bounded by a free plane surface, the sources being located at an inner point in the half-space. A transient regime of generation and propagation of seismic waves is identified, as distinct from the stationary regime of elastic vibrations. This is another new concept. It is shown that elementary seismic sources produce (double-shock) spherical-shell waves (in the wave region), which are the well-known P and S waves associated with the feeble tremor in the recorded seismograms. Their mathematical expression, derived here from the tensorial force, differs from known, particular cases. These waves are called here collectively ‘primary’ waves. It is shown that the primary waves interact with the surface of the half-space, where they give rise to ‘secondary’ wave sources, placed on the surface. The secondary waves generated by the secondary sources (which may be called ‘surface seismic radiation’) are estimated here in a simplified model. It is shown that the secondary waves have a delay time in comparison with the primary waves and give rise to a main shock and a long seismic tail, in qualitative agreement with the seismic records. The secondary wave introduced here is a new concept; the main shock and its long tail derived here are elements of novelty. Similarly, the secondary waves generated by an internal discontinuity in the elastic properties of the half-space (an interface parallel with the free surface) are also estimated; it is shown that the discontinuity reduces appreciably the singular main shock on the free surface of the homogeneous half-space.

Authors:
Apostol B.F., Bălan S.F., Ionescu C.

Abstract:
The effects of the earthquakes on buildings and the concept of seismic base isolation are investigated by using the model of the vibrating bar embedded at one end. The normal modes and the eigenfrequencies of the bar are highlighted and the amplification of the response due to the excitation of the normal modes (eigenmodes) is computed. The effect is much enhanced at resonance, for oscillating shocks which contain eigenfrequencies of the bar. Also, the response of two linearly joined bars with one end embedded is calculated. It is shown that for very different elastic properties the eigenfrequencies are due mainly to the "softer" bar. The effect of the base isolation in seismic structural engineering is assessed by formulating the model of coupled harmonic oscillators, as a simplified model for the structure building-foundation viewed as two coupled vibrating bars. The coupling decreases the lower eigenfrequencies of the structure and increases the higher ones. Similar amplification factors are derived for coupled oscillators at resonance with an oscillating shock.

Authors:
Ardeleanu L.

Abstract:
An approach based on high-frequency waveform modeling is proposed to estimate 1-D (depth-dependent) models of the quality factor of the medium Q in the area located at the bending of the Eastern Carpathians. The algorithm is a non-linear inversion in which the normalised amplitude spectra of local records of low-tomoderate magnitude earthquakes are compared with the synthetic signal spectra, generated for point sources with the same location and mechanism as the recorded events. The best fitting Q-models are determined by minimizing the sum of squares of logarithmic residuals between theoretical and observed spectra. Several tests investigating the effect of the uncertainty of earthquake mechanism and hypocenter location on the resolution of the retrieved attenuation structures are presented.

Authors:
Armaș I.¸ Toma-Dănilă D., Ionescu R., Gavriș A.

Abstract:
Recent seismic events show that urban areas are increasingly vulnerable to seismic damage, which leads to unprecedented levels of risk. Cities are complex systems and as such their analysis requires a good understanding of the interactions between space and the socioeconomic variables characteristic of the inhabitants of urban space. There is a clear need to develop and test detailed models that describe the behavior of these interactions under seismic impact. This article develops an overall vulnerability index to seismic hazard based on a spatial approach applied to Bucharest, Romania, the most earthquake-prone capital in the European Union. The methodology relies on: (1) spatial post-processed socioeconomic data from the 2011 Romanian census through multicriteria analysis; and (2) analytical methods (the Improved Displacement Coefficient Method and custom-defined vulnerability functions) for estimating damage patterns, incorporated in a GIS environment. We computed vulnerability indices for the 128 census tracts of the city. Model sensitivity assessment tested the robustness of spatially identified patterns of building vulnerability in the face of uncertainty in model inputs. The results show that useful seismic vulnerability indices can be obtained through interdisciplinary approaches that enhance less detailed datasets, which leads lead to better targeted mitigation efforts.

Authors:
Bălan S. F., Apostol B. F., Ionescu C.

Abstract:
The purpose of the paper is to show the great influence of nonlinear seismology in the analysis of the soil deposit response. Some elements about nonlinear seismology, the complexity of the seismic phenomenon are presented, and how we perceive seismic input for constructions at the surface of the earth. Further is presented the nonlinear behaviour of soil deposits during strong earthquakes as it results from resonant column tests (in laboratory) and from the spectral amplification factors (in situ records). The resonance phenomenon between natural period of a structure and soil deposit during strong earthquakes is analysed. All these studies have in common nonlinear behaviour of the soil deposit during strong earthquakes, in fact, the site where a new construction is built or an old one is rehabilitated and needs an optional assessment for mitigation seismic risk. All these studies stand up in supporting nonlinear seismology, the seismology of the XXI-st century.

Authors:
Bălă A., Răileanu V.

Abstract:
Seismicity in western part of Romania is the result of tectonic evolution, which created a fragmented structure at the crystalline basement level, with blocks that have suffered differential movements due to general tectonic stress in the area, and due to secondary factors such as erosion or lateral variations in density. Some of the faults formed during development of the units under survey were reactivated later in recent periods of stress and became seismogenic faults. The present paper is an analysis of tectonics and seismicity in the western part of Romania (Pannonian depression and Transylvanian Basin, and the Apuseni Mountains Orogen). Several maps interpreted by different Romanian authors on local tectonics are presented and a final map with active faults in the region of study is constructed. The first part is a summary of the stress field in the Earth crust and tectonic evolution of the Carpathian area with particular reference to the units analyzed. Each unit is analyzed based on published sources, finally emphasizing the peculiarities of each area and tectonic fault lines known in particular. In a later chapter is a summary of information on the behavior of the stress field of study areas and seismicity zone, the range of magnitude and hypocenter depths registered with mention of the most significant events occurring over time and relative to areas where they were concentrated. In the last chapter fault systems in the study region are presented, their peculiarities as they appear in the available studies projected on the local tectonic structure for each of the areas under examination. Results are reported using the tectonic map of Romania, on which epicenters of earthquakes in the catalog ROMPLUS (NIEP Catalog) by the end of 2010 are projected.

Authors:
Bălă A., Toma-Dănilă D., Tătaru D., Grecu B.

Abstract:
In the years 1999 - 2000, two regional seismic refraction lines were performed in close cooperation with German partners from the University of Karlsruhe. One of these lines is Vrancea 2001, with 420 km in length, almost half of them recorded in Transylvanian Basin. The structure of the crust along the seismic line revealed a very complicated crustal structure beginning with Eastern Carpathians and continuing in the Transylvanian Basin until Medias. As a result of the development of the National Seismic Network in the last ten years, more than 100 permanent broadband stations are now continuously operating in Romania. Complementary to this national dataset, maintained and developed in the National Institute for Earth Physics, new data emerged from the temporary seismologic networks established during the joint projects with European partners in the last decades. The data gathered so far is valuable both for seismology purposes and crustal structure studies, especially for the western part of the country, where this kind of data were sparse until now. Between 2009 and 2011, a new reference model for the Earth's crust and mantle of the European Plate was defined through the NERIES project from existing data and models. The database gathered from different kind of measurements in Transylvanian Basin and eastern Pannonian Basin were included in this NERIES model and an improved and upgraded model of the Earth crust emerged for western part of Romania. Although the dataset has its origins in several periods over the last 50 years, the results are homogeneous and they improve and strengthen our image about the depth of the principal boundaries in the crust. In the last chapter two maps regarding these boundaries are constructed, one for mid-crustal boundary and one for Moho. They were build considering all the punctual information available from different sources in active seismic and seismology which are introduced in the general maps from the NERIES project for Romania. The depths maps in the study region are presented with all their regional peculiarities as they appear, projected on the local tectonic structure for the area under examination.

Authors:
Borleanu F., De Siena L., Thomas C., Popa M., Radulian M.

Abstract:
The Vrancea region, located at the southeastern edge of the Carpathians arc bend, is a region of intense seismicity, whose major earthquakes produce hazard in southeastern Europe. Despite the consequent focus of the geophysical and geological community on providing accurate structural and dynamical models of Vrancea, these are still subject to numerous controversies and debates. In the present study, we use intermediate-depth seismicity recorded by the broadband stations of the Romanian Seismic Network between 2009 and 2011 to measure S-wave peak delay times and late-time coda quality factors. After mapping these two quantities in space, a cluster analysis provides a quantitative structural interpretation of the region in terms of different attenuation mechanisms affecting the seismic wave field, i.e. seismic scattering and seismic absorption. The results show that scattering is higher west and northwest of Vrancea, while absorption dominates in the Focsani Basin, located in the forearc region. In general, we obtain higher absorption in stable regions, with patterns emphasized at high-frequency affected by the presence of hydrocarbons and natural gas reservoirs in the upper crustal layers. Regions characterized by active seismicity and structural heterogeneity show higher scattering, spatially correlated with the highest velocity contrasts and the lowest density. The high-frequency scattering/absorption contrasts obtained using the cluster analysis depict a southwest-to-northeast lithospheric contrast, following the epicentral trend of Vrancea earthquakes, and characteristic of either lithospheric subduction or delamination. Low-frequency cluster analysis results, sampling deeper Earth layers, mark a unique high-absorption trend perpendicular to the epicentral trend, feasibly linked to Neogene volcanism, and induced by the back-arc mantle upwelling. Its most recent expression is Ciomadul volcano, located at the northwestern limit of the absorption trend.

Authors:
Bratoșin D., Apostol B. F., Bălan S. F.

Abstract:
An appropriate estimation of the site-structure resonance period involves the nonlinear dependence of the site natural period on strain or loading level. The site materials are assumed in this paper to be nonlinear viscoelastic materials, modeled by a nonlinear Kelvin-Voigt model. By using resonant column tests we can quantify the nonlinear dependence of the site natural period in the normalized form Tn=Tn(∙) , such that the nonlinear site natural function acquires the form: Tg(∙)=T0⋅Tn(∙), with T0 being the fundamental period from seismic recordings. The method consists in laboratory experiments on soils samples for a site with sufficient seismic records. In order to mitigate seismic risk, the structures fundamental period must be outside the range of the computed nonlinear values.

Authors:
Craiu A., Craiu M., Diaconescu M., Mărmureanu A.

Abstract:
An unusual seismic swarm started on September 23, 2013, close to Galati city, in Izvoarele region (Romania), and lasted until November 12, 2013. 406 earthquakes were recorded during several phases of seismic activity. The strongest events—a magnitude 3.9 earthquake, occurred on September 29, and two ML 3.8 shocks, occurred on October 3 and 4, respectively, were accompanied by specific seismicity bursts. The seismogenic region of the swarm is situated between two main crustal faults, which builds up the primary fault system, oriented SE–NW: New Trotus Fault (at the limit between North Dobrogea and Scythian Platform) to the North and east, and Peceneaga Camena fault (which separates North Dobrogea block from the Moesian Platform) to the South. The epicentral zone belongs to a complex tectonic area, in which a secondary fault system—lying NE–SW, perpendicular to the primary system—is also present. The focal mechanisms show normal faulting, with an important strike-slip component, one of the nodal planes being oriented roughly in a NE–SW direction. The objective of this study is to investigate the seismic swarm recorded in a new seismic area of Romania, near the town Galati in Izvoarele region. We show detailed hypocentral location, focal mechanisms and the correlation between seismicity and tectonic structures.

Authors:
Constantin A.P., Moldovan I.A., Lavigne F., Grancher D., Partheniu R.

Abstract:
Tsunami is one of the major natural hazards presenting significant flood risk for coastal communities and therefore, increasing the society resilience to this phenomena in exposed areas is very important for minimizing damage and possible destructive effects on the environment in these areas. In the frame of the EC Programme-FP7 ASTARTE project (Assessment, STrategy And Risk reduction for Tsunamis in Europe), we conducted a questionnaire survey among people living, working, or visiting Eforie Nord site. The tsunami questionnaire has been translated in Romanian language, the questions referring to: interviewee's relation to Eforie Nord site, information about interviewed people, tsunami hazard knowledge/risk perception, evacuation issue, awareness of the existing warning system, information, and communication. The results obtained after the survey confirm that coastal communities from Romania are not resilient to tsunami hazard. Our respondents have mentioned from natural and anthropic types of hazards, the tsunami as third rank in Eforie Nord test site, coming after earthquakes and storms. Whatever the respondent?s status (i.e. local population, or tourists), earthquakes and sea withdrawal are cited as tsunami warning signs by 62% and 60% of the respondents, respectively. Regarding the perception of a future tsunami event in Eforie Nord, 36.3% of the respondents think that the place could be affected by a tsunami and the tsunami wave could reach more than 2-5 meters (heights cited by approx. 14% of respondents) or even more than 5-10 meters (values cited by 15% of interviewed people).

Authors:
Darbyshire F., Bastow I. D., Petrescu L., Gilligan A., Thompson D. A.

Abstract:
The Precambrian core of North America was assembled in the Proterozoic by a series of collisions between Archean cratons. Among the orogenic belts, two stand out due to their significant spatial extent. The Paleoproterozoic Trans-Hudson Orogen (THO) and Mesoproterozoic Grenville Orogen extend for thousands of kilometers along strike and hundreds of kilometers across strike. Both have been compared to the present-day Himalayan-Karakoram-Tibetan Orogen (HKTO). Over the last 20–30 years, active and passive source seismic studies have contributed a wealth of information about the present-day crustal structure and composition of the two orogens in Canada. The Proterozoic orogenic crust is generally thicker than that of neighboring Archean terranes, with a more variable Moho character, ranging from relatively sharp to highly diffuse. Both orogens have a prominent high-velocity lower crustal layer, consistent with long-term preservation of a partially eclogitized root at the base of the crust and similar to that inferred beneath the western HKTO. Crustal structure in the northern THO strongly resembles the lower crustal structure of the HKTO, suggesting that Moho depths may have reached 60–70 km when the orogen was active. A prominent midcrustal discontinuity beneath the central Grenville Province and changes in the patterns of seismic anisotropy in the THO crust beneath Hudson Bay provide geophysical evidence that lower crustal flow likely played a role in the evolution of both orogens, similar to that inferred beneath the present-day HKTO. The seismic evidence from Canada supports the notion of tectonic uniformitarianism, at least as far back as the Paleoproterozoic.

Authors:
Lizurek G., Mărmureanu A., Wiszniowski J.

Abstract:
Bucharest, with a population of approximately 2 million people, has suffered damage from earthquakes in the Vrancea seismic zone, which is located about 170 km from Bucharest, at a depth of 80–200 km. Consequently, an earthquake early warning system (Bucharest Rapid earthquake Early Warning System or BREWS) was constructed to provide some warning about impending shaking from large earthquakes in the Vrancea zone. In order to provide quick estimates of magnitude, seismic moment was first determined from P-waves and then a moment magnitude was determined from the moment. However, this magnitude may not be consistent with previous estimates of magnitude from the Romanian Seismic Network. This paper introduces the algorithm using P-wave spectral levels and compares them with catalog estimates. The testing procedure used waveforms from about 90 events with catalog magnitudes from 3.5 to 5.4. Corrections to the P-wave determined magnitudes according to dominant intermediate depth events mechanism were tested for November 22, 2014, M5.6 and October 17, M6 events. The corrections worked well, but unveiled overestimation of the average magnitude result of about 0.2 magnitude unit in the case of shallow depth event (H < 60 km). The P-wave spectral approach allows for the relatively fast estimates of magnitude for use in BREWS. The average correction taking into account the most common focal mechanism for radiation pattern coefficient may lead to overestimation of the magnitude for shallow events of about 0.2 magnitude unit. However, in case of events of intermediate depth of M6 the resulting M w is underestimated at about 0.1–0.2. We conclude that our P-wave spectral approach is sufficiently robust for the needs of BREWS for both shallow and intermediate depth events.

Authors:
Manea E. F., Michel C., Hobiger M., Fah D., Cioflan C. O., Radulian M.

Abstract:
During large earthquakes generated at intermediate depth in the Vrancea seismic zone, the ground motion recorded in Bucharest (Romania) is characterized by predominant long periods with strong amplification. Time–frequency analysis highlights the generation of low frequency surface waves (<1 Hz) for sufficiently strong and superficial events. This phenomenon has been explained by the influence of both source mechanism (radiation pattern, directivity effects) and mechanical properties of the local geological structure (geological layering and geometry). The main goal of our study is to better characterize and understand the seismic wavefield produced by earthquakes in the area of Bucharest, taking into account its location in the centre of the Moesian Platform, a large sedimentary basin (450 km long, 300 km wide and up to 20 km deep). To this aim, we identify the contribution of different seismic surface waves, such as the ones produced at the edges of this large sedimentary basin or multipath interference waves (Airy phases of Love and Rayleigh waves), on ground motion. The data from a 35 km diameter array (URS experiment) were used. The array was installed by the National Institute for Earth Physics in cooperation with the Karlsruhe Institute for Technology and operated during 10 months in 2003 and 2004 in the urban area of Bucharest and adjacent zones. The earthquake wavefield recorded by the URS array was analysed using the MUSIQUE technique. This technique analyses the three-component signals of all sensors of a seismic array together. The analysis includes 19 earthquakes with epicentral distances from 100 to 1560 km and with various backazimuths with enough energy at low frequencies (0.1–1 Hz), within the resolution range of the array. For all events, the largest portion of energy is arriving from the source direction and the wavefield is dominated by Love waves. The results of the array analyses clearly indicate a significant scattering corresponding to 2-D or 3-D effects of the Moesian Platform. The azimuthal distribution shows that the scattering comes primarily from the southern and northern edges of the basin. The Airy phase of Love waves was clearly identified as the main contributor in the range of the fundamental frequency of resonance of the basin (0.15–0.25 Hz), with directionality along the backazimuth and its opposite direction. Moreover, two further distinct frequency bands around 0.4 and 0.7 Hz with higher amplitudes were identified. Their complex nature is a combination of the higher modes of Rayleigh waves, Airy phases of Love waves and SH waves. Love and Rayleigh wave dispersion curves were successfully retrieved by combining the information of all events and show a good match with the ones obtained using ambient vibrations. Additionally, the first higher mode of Rayleigh waves could be retrieved using data from earthquakes. Also, the prograde and retrograde Rayleigh wave ellipticity was computed.

Authors:
Mărmureanu Gh., Manea E. F., Cioflan C.O., Mărmureanu A., Ionescu C., Toma-Dănilă D.

Abstract:
Devastating – and, in some sense, unforeseen – earthquakes in Nepal, Japan, New Zealand, Haiti, Sumatra and elsewhere have triggered in last time a heated debate about the legitimacy and limitations of Probabilistic Seismic Hazard Assessment (PSHA). This method is a pure numerical creation, as it was developed from mathematical statistics and not based on earthquake physics. An important source of errors came from one of its key component: the Ground Motion Prediction Equation (GMPE), which describes a relationship between a ground motion parameter (PGA etc.), magnitude M, distance R., without taking into account the nonlinear behavior of site soils during strong earthquakes. In order to capture these effects, the spectral amplification factors (SAF) were computed for the last recorded Vrancea intermediate-depth events showing a decrease with the increase of earthquake magnitude of earthquakes and these values are far of those given by R.G.1.60 of the U. S. Atomic Energy Commission and IAEA Vienna. These SAF were used by NIEP, as alternative analysis, for NPP Cernavoda (Romania) in the last “2011 STRESS TEST” asked by IAEA Vienna after Japan's strong earthquake (Mw = 9.0).

Authors:
Moldovan I.A., Diaconescu M., Partheniu R., Constantin A.P., Popescu E., Toma-Dănilă D.

Abstract:
The paper has as its final goal the probabilistic assessment of seismic hazard in the Black Sea area as input for the tsunami hazard evaluation. Maximum and most expected magnitudes and their recurrence periods have been computed for all defined seismogenic sources from the marine area, and hazard curves have been plotted.

Authors:
Oikonomou C., Haralambous H., Moldovan I. A., Greculeasa R.

Abstract:
Ionospheric TEC (Total Electron Content) variations and Low Frequency (LF) signal amplitude data prior to three large earthquakes (M ≥ 6) in Greece was analyzed using observations from the Global Navigation Satellite System (GNSS) and the European INFREP (International Network for Frontier Research on Earthquake Precursors) networks respectively, aiming to detect potential ionospheric anomalies related to these events and describe their characteristics. For this, spectral analysis on TEC data and terminator time method on LF data were applied. It was found that TEC perturbations appeared few days (1–7) up to a few hours before the events lasting around 2–3 hours, with periods 20 and 3–5 minutes which could be associated with the impending earthquakes. In addition, in all three events, the sunrise terminator times were delayed approximately 20–40 min a few days prior and during the earthquake day.

Authors:
Oros E., Popa M., Rogozea M.

Abstract:
The main task of the presented study is to elaborate a set of relations of mutual conversion macroseismic intensity - magnitude, necessary for the calibration of the historical crustal earthquakes produced in the Intra - Carpathian region of Romania, as a prerequisite for homogenization of the parametric catalogue of Romanian earthquakes. To achieve the goal, we selected a set of earthquakes for which we have quality macroseismic data and the Mw moment magnitude obtained instrumentally. These seismic events were used to determine the relations between the Mw and the peak/epicentral intensity, the isoseist surface area for I=3, I=4 and I=5: Mw = f (Imax / Io), Mw = f (Imax / Io, h), Mw = f (A3, A4; A5). We investigated several variants of such relationships and combinations, taking into account that the macroseismic data necessary for the re-evaluation of historical earthquakes in the investigated region are available in several forms. Thus, a number of investigations provided various information resulted after revising initial historical data: 1) Intensity data point (IDP) assimilated or not with the epicentre intensity after analysis of the correlation level with recent seismicity data and / or active tectonics / seismotectonics, 2) Sets of intensities obtained in several localities (IDPs) with variable values having maxims that can be considered equal to epicentral intensity (Io), 3) Sets of intensities obtained in several localities (IDPs) but without obvious maximum values, assimilable with the epicentral intensity, 4) maps with isoseismals, 5) Information on the areas in which the investigated earthquake was felt or the area of perceptiveness (e.g. I = 3 EMS during the day and I = 4 EMS at night) or the surfaces corresponding to a certain degree of well-defined intensity. The obtained relationships were validated using a set of earthquakes with instrumental source parameters (localization, depth, Mw). These relationships lead to redundant results meaningful in the process of estimating the quality and credibility of the primary data used (e.g. IDPs, isoseismals) and in the correct determination of Mw.

Authors:
Petrescu L., Darbyshire F., Bastow I., Totten E., Gilligan A.

Abstract:
The thick, seismically fast lithospheric keels underlying continental cores (cratons) are thought to have formed in the Precambrian and resisted subsequent tectonic destruction. A consensus is emerging from a variety of disciplines that keels are vertically stratified, but the processes that led to their development remain uncertain. Eastern Canada is a natural laboratory to study Precambrian lithospheric formation and evolution. It comprises the largest Archean craton in the world, the Superior Craton, surrounded by multiple Proterozoic orogenic belts. To investigate its lithospheric structure, we construct a frequency-dependent anisotropic seismic model of the region using Rayleigh waves from teleseismic earthquakes recorded at broadband seismic stations across eastern Canada. The joint interpretation of phase velocity heterogeneity and azimuthal anisotropy patterns reveals a seismically fast and anisotropically complex Superior Craton. The upper lithosphere records fossilized Archean tectonic deformation: anisotropic patterns align with the orientation of the main tectonic boundaries at periods ≤110 s. This implies that cratonic blocks were strong enough to sustain plate-scale deformation during collision at 2.5 Ga. Cratonic lithosphere with fossil anisotropy partially extends beneath adjacent Proterozoic belts. At periods sensitive to the lower lithosphere, we detect fast, more homogenous, and weakly anisotropic material, documenting postassembly lithospheric growth, possibly in a slow or stagnant convection regime. A heterogeneous, anisotropic transitional zone may also be present at the base of the keel. The detection of multiple lithospheric fabrics at different periods with distinct tectonic origins supports growing evidence that cratonization processes may be episodic and are not exclusively an Archean phenomenon.

Authors:
Popescu E., Plăcintă A. O., Radulian M., Borleanu F., Diaconescu M., Popa M.

Abstract:
The seismic activity recorded in the Eastern Carpathians is poor and scarce (a few hundreds of small-to-moderate earthquakes in the Romanian catalogue over the last century). The installation in 2002 of the high-performance Bucovina (BURAR) array in the Eastern Carpathians area contributed to a significant growth of the capacity to monitor local seismicity. As a consequence, the earthquake sequence occurred between 24 June and 1 July 2011 close to the BURAR array is the best seismic data set ever recorded for this area. The location of the events using all the available data provided by the real-time seismic network of the National Institute for Earth Physics shows a NE-SW alignment along the western edge of Avrămeşti - Suceava fault. This fault is crossing the Carpathian Foredeep underthrusting the foreland units to the orogeny area. The distribution of the first P-wave polarities is fitting the geometry of this fault, indicating predominant strike-slip faulting, with right-lateral movement. The compression axis oriented E-W is in agreement with the stress field characterizing the region. We applied spectral ratios and empirical Green’s function methods to estimate the source parameters (corner frequency, seismic moment, source duration, rise time) for the events with moment magnitudes higher than 2.5 recorded within this sequence. The results show a simple fracture model for the main shock of 24 June 2011 and a constant stress drop scaling. Source parameter scaling relationships fit well the results obtained for other regions along the South-Eastern Carpathians and those which are typical for intra-continental areas.

Authors:
Popescu E., Plăcintă A. O., Borleanu F., Radulian M.

Abstract:
The Vrancea seismic nest, located at the South-Eastern Carpathians Arc bend, in Romania, is a well-confined cluster of seismicity at an intermediate depth (60 – 180 km). During the last 100 years, four major shocks were recorded in the lithosphere body descending almost vertically beneath the Vrancea region: 10 November 1940 (Mw 7.7, depth 150 km), 4 March 1977 (Mw 7.4, depth 94 km), 30 August 1986 (Mw 7.1, depth 131 km) and a double shock on 30 and 31 May 1990 (Mw 6.9, depth 91 km and Mw 6.4, depth 87 km, respectively). The probability of repeated earthquakes in the Vrancea seismogenic volume is relatively large taking into account the high density of foci. The purpose of the present paper is to investigate source parameters and clustering properties for the repetitive earthquakes (located close each other) recorded in the Vrancea seismogenic subcrustal region. To this aim, we selected a set of earthquakes as templates for different co-located groups of events covering the entire depth range of active seismicity. For the identified clusters of repetitive earthquakes, we applied spectral ratios technique and empirical Green's function deconvolution, in order to constrain as much as possible source parameters. Seismicity patterns of repeated earthquakes in space, time and size are investigated in order to detect potential interconnections with larger events. Specific scaling properties are analyzed as well. The present analysis represents a first attempt to provide a strategy for detecting and monitoring possible interconnections between different nodes of seismic activity and their role in modeling tectonic processes responsible for generating the major earthquakes in the Vrancea subcrustal seismogenic source.

Authors:
Năstase E.I., Muntean A., Ionescu C., Mocanu V., Ambrosius B.A.C

Abstract:
A decade of improvements and new development of tools for observation statistics, standard point positioning, clock-jumps and cycle-slip detection and other interruptions over all constellations, frequencies and signals, satellite elevations and azimuths, elevation-specific histograms, satellite ascending/descending times for horizon and user elevation cut-off, pseudo-range multipath and noise, carrier-phase signal-to-noise ratio, data gaps and small data pieces and other useful lists and statistics allow us to analyze in detail the GNSS data collected for one of the main research subjects resulted from the September 2013 unique seismic swarm event that occurred in Romania. Open-source software such as: G-Nut/Anubis (Geodetic Observatory Pecn?), RTKLIB, gLAB (European Space Agency) and commercial software like: Leica Spider QC, Leica Geo Office are used for quality control over all available data of the Ph.D. thesis called ?An integrated GNSS and seismotectonic study of the NW Galati seismogenic area?. The main purpose of the paper is currently the quantity and quality monitoring of all available GNSS data achieved in 4 years of continuous monitoring along with the solutions obtained from the 4 GPS measuring campaigns (2013-2016), i.e. signals, frequencies and satellite constellations.

Authors:
Radulian M., Popescu E., Plăcintă A. O.

Abstract:
The Vrancea seismogenic area, located in the South-Eastern Carpathians in Romania, is generating extreme destructive subcrustal earthquakes in Europe. The largest events generated in the last ten years in the Vrancea subcrustal domain occurred on May 14, 2005 (01:53, 45.64o N, 26.53o E, h=149 km, Mw = 5.5), April 25, 2009 (17:18, 45.68oN, 26.62o E, h=110 km, Mw = 5.4) and October 6, 2013 (01:37, 45.67oN, 26.58oE, h=135 km, Mw = 5.2). The purpose of the present paper is to determine the seismic source parameters of these events using the Empirical Green’s function deconvolution and spectral ratios techniques. To this aim, we selected a set of empirical Green’s functions in association with the three main events, as co-located events with similar focal mechanisms. The large number of high-quality waveforms recorded for the main shock-EGF pairs provides a good database to constrain source parameters, even though the events are relatively small and are recorded practically in the far field. The seismic moment - source radius scaling and stress drop values range, match well the results as previously obtained on larger data sets.

Authors:
Tătaru D., Zaharia B., Grecu B.

Abstract:
More and more steps have been made by research to fulfill society needs. Among different science domains geoscience education community experience an increase in interest of getting more and more engaged in children formal and informal didactic roadmap. Not few are the spaces dedicated for undergoing didactic activities inside research institutes. Create through a research and outreach project (www.roeduseis.ro), the Seismolaboratory created inside the Romanian National Institute for Earth Physics serve the purpose of disseminating information about earth and earthquakes contextualized and adapted for pupils, students and also teachers. Laboratory space can be used both as a physical and virtual space for delivering a lesson. Starting with 2014 many children, all ages, had the opportunity to visualize as well as experiment thinks that help them understand why earthquake occurs, what are seismic waves and how travel through the layer of the Earth, what “magic tricks” researchers use to precisely locate and measure the strength of such a natural phenomenon. Firstly design as an outreach initiative, slowly the initiative was regarded and received by schools as a form of informal education for science. Theoretical facts presented side by side with hands-on-experiment, interactive games and support materials shift from informing about earthquakes to learning about geoscience. A natural follow up was to develop materials (books, brochures, information and activity sheets) to be also used in school classes. A collection of educational materials entitled“ Earthquakes and their effects” was trying to bring in one place, in a mix of theoretical introductory chapters followed by exercises and proposed experiments, the interdisciplinary characteristic of the subject (earthquakes). After being tested in couple of high school classes the educational materials had being proper “translated” in a an interdisciplinary school choice optional for secondary and high schools (physics-geography-ICT) and applied further in 10 more classes, mainly secondary and high school level. Even if the triggering initiative ended, the impact go far beyond the lifetime of the project and is among the initiatives that bring closer research to school environment by exposing students to science-related topics and progressively advanced science education.

Authors:
Toader V. E., Moldovan I. A., Marmureanu A., Dutta P. K., Partheniu R., Nastase E.

Abstract:
Our multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains) includes radon concentration monitoring in five stations. We focus on lithosphere and near surface low atmosphere phenomena using real-time information about seismicity, + / – ions, clouds, solar radiation, temperature (air, ground), humidity, atmospheric pressure, wind speed and direction, telluric currents, variations of the local magnetic field, infrasound, variations of the atmospheric electrostatic field, variations in the earth crust with inclinometers, electromagnetic activity, CO2 concentration, ULF radio wave propagation, seismoacoustic emission, animal behavior. The main purpose is to inform the authorities about risk situation and update hazard scenarios. The radon concentration monitoring is continuously with 1 hour or 3 hours sample rate in locations near to faults in an active seismic zone characterized by intermediate depth earthquakes. Trigger algorithms include standard deviation, mean and derivative methods. We correlate radon concentration measurements with humidity, temperature and atmospheric pressure from the same equipment. In few stations we have meteorological information, too. Sometime the radon concentration has very high variations (maxim 4 535 Bq/m from 106 Bq/m) in short time (1–2 days) without being accompanied by an important earthquake. Generally the cause is the high humidity that could be generated by tectonic stress. Correlation with seismicity needs information from minimum 6 month in our case. For 10 605 hours, 618 earthquakes with maxim magnitude 4.9 R, we have got radon average 38 Bq/m and exposure 408 111 Bqh/m in one station. In two cases we have correlation between seismicity and radon concentration. In other one we recorded high variation because the location was in an area with multiple faults and a river. Radon can be a seismic precursor but only in a multidisciplinary network. A pair of ions counters (positive and negative) work together in few stations. The anomalies for short or long period of time should be correlated with local environment factors (e.g. humidity)

Authors:
Toma-Dănilă D., Armaș I.

Abstract:
Seismic loss estimation analysis for large cities is a very demanding yet necessary task; the modelling of such complex systems requires first of all insightful input data at good resolution, referring to local effects, buildings and socio-economic aspects. Also, the implementation of less empirical estimation methods is needed. Until recently, these requirements could not be fulfilled for Bucharest, the capital city in the European Union which is most at risk due to earthquakes. Based on 2011 and 2002 census data, standardized according to the framework of the Near-real time System for Estimating the Seismic Damage in Romania (SeisDaRo) through a unique approach, and on relevant hazard scenarios, we estimate for the first time the building damage at census tract scale. The methodology applied relies on 48 vulnerability curves for buildings, on the Improved Displacement Coefficient Analytical Method included in the SELENA software for computing damage probabilities and on deterministic seismic hazard scenarios, including the maximum possible earthquake. By using overlay analysis with satellite imagery and a new methodology integrated in GIS we show how results can be enhanced, reflecting more localized characteristics. Best practices for seismic risk mapping are also expressed. The results are promising and contribute to mitigation efforts in Bucharest.

Authors:
Toma-Dănilă D., Cioflan C.O.

Abstract:
ShakeMaps are one of the most applicative products of seismological research and monitoring, becoming available minutes after earthquakes. They are maps depicting the ground shaking produced by an earthquake and the estimated intensity distribution, being extremely useful for authorities, population, private sector and researchers too. However, the outcome of the result ? consisting of easy to read maps representing the potential area affected, often hides the fact that many compromise decisions and uncertainties are included in the methodology. Such decisions are related for example to the way real-data is handled (some values can be modified more or less, in order to match ground-motion prediction equations - GMPE, at rock or soil level) or the way GMPEs or interpolation methods are selected. In Romania, the ShakeMap system developed by USGS is implemented, but due to the characteristics of the Vrancea Intermediate-Depth Source (which is the most active and hazardous in the country), there is an apparent mismatch with the typical algorithm developed mainly for crustal earthquakes. That is why we chose to replicate the ShakeMap methodology partially, turn it into an open-source Matlab code and test new refinement procedures that can be of use in other cases of custom needed implementation. Among the new features that we describe in this paper and for which we present results in comparison are: i) the integration of new GMPE?s for Vrancea earthquakes; ii) a new azimuthal dependent procedure for proper GMPE selection considering real recordings; iii) a dynamic module for integrating crowd-sourced intensity data filtered adequately and iv) new types of GIS map representations. In Romania, the seismic network operated by NIEP consists of more than 140 real-time seismic stations; in the new ShakeMap development, we include new rules for discriminating between reliable and erroneously reported values of macroseismic intensities.

Authors:
Zaharia B., Grecu B., Popa M., Oros E., Radulian M.

Abstract:
The inner part of the Carpathians in Romania belongs to the Carpathians-Pannonian system bordered by the Eastern Carpathians to the north and east, Southern Carpathians to the south and Pannonian Basin to the west. It is a complex tectonic region with differential folding mechanisms, post-collisional kinematics, rheology and thermal properties, including within its area the Apuseni Mountains and the Transylvanian Basin. The purpose of this study is to map the 3-D structure of the crust over this region on the basis of local earthquake data. Input data were recorded during the South Carpathian Project (2009–2011), a successful collaboration between the Institute of Geophysics and Tectonics of the University of Leeds and the National Institute for Earth Physics (NIEP), Romania. A temporary array of 32 broadband seismic stations (10 CMG-40T, 8 CMG-3T and 14 CMG-6TD) was installed across the western part of Romania (spaced at 40 to 50 km intervals) during the project. In addition, 25 stations deployed in the eastern Hungary and Serbia was considered. P- and S-wave arrivals are identified for all the selected events (minimum 7 phases per event with reasonable signal/noise ratio). All the events are first relocated using Joint Hypocentre Determination (JHD) technique. Then the well-located events were inverted to determine the crustal structure using LOTOS algorithm. The lateral variations of the crustal properties as resulted from the tomography image are interpreted in correlation with the station corrections estimated by JHD algorithm and with the post-collisional evolution of the Carpathians-Pannonian system.

Authors:
Zoran M.A., Savastru R.S., Savastru D.M., Șerban F.S., Teleagă D.M., Mateciuc D.N.

Abstract:
Time series analysis of GPS (Global Positioning Systems) and InSAR (Interferometric Synthetic Aperture Radar) data are important tools for Earth's surface deformation assessment, which can result from a wide range of geological phenomena like as earthquakes, landslides or ground water level changes. The aim of this paper was to identify several types of earthquake precursors that might be observed from geospatial data in Vrancea seismogenic region in Romania. Continuous GPS Romanian network stations and few field campaigns data recorded between 2005-2012 years revealed a displacement of about 5 or 6 millimeters per year in horizontal direction relative motion, and a few millimeters per year in vertical direction. In order to assess possible deformations due to earthquakes and respectively for possible slow deformations, have been used also time series Sentinel 1 satellite data available for Vrancea zone during October 2014 till October 2016 to generate two types of interferograms (short-term and medium- term). During investigated period were not recorded medium or strong earthquakes, so interferograms over test area revealed small displacements on vertical direction (subsidence or uplifts) of 5-10 millimeters per year. Based on GPS continuous network data and satellite Sentinel 1 results, different possible tectonic scenarios were developed. The localization of horizontal and vertical motions, fault slip, and surface deformation of the continental blocks provides new information, in support of different geodynamic models for Vrancea tectonic active region in Romania and Europe.

Authors:
Constantin A. P., Partheniu R., Moldovan I. A., Pantea A.

Abstract:
On April 25, 2009, at 20:18:48 (local hour) the Romanian territory was shaken by a moderate size earthquake centred beneath the bending area of the southeastern Carpathians, in the Vrancea seismogenic region (Romania). In the present paper we present an intensity map, macroseismic intensities, and community observations of effects for the MW = 5.4 Vrancea subcrustal earthquake of 25 April, 2009. For many locations, for the estimation of the macroseismic intensities besides questionnaires other type of sources such as press reports, internet were used. The highest intensity assigned for this Vrancea earthquake was VI MSK, estimated for eleven locations, situated in the north-eastern part of Vrancea seismogenic zone, which include parts from Vrancea, Bacau, and Galati counties. At the lowest intensities, the 2009 earthquake was felt to a distance of 500 km from the epicenter, in Rep. of Moldova, Bulgaria, Ukraine, and Serbia. A non-uniform distribution of intensity resulted in locations in different directions from the epicenter. A scatter of as much as one to two intensity units were observed for places situated very close. The comparison of the intensity areas for the October 27, 2004, and April 25, 2009- moderate subcrustal earthquakes of the Vrancea seismogenic zone was performed.

Authors:
Poiată N., Miyake H.

Abstract:
We estimated the parameters of strong motion generation areas and simulated broadband ground motions for the moderate October 27, 2004 (M w 5.8) and damaging March 4, 1977 (M w 7.4) Vrancea (Romania) intermediate-depth subduction earthquakes using the empirical Green’s function method. The method allows the simulation of ground motions in a broadband frequency range by summing up the subevent records, corresponding to small magnitude events in the near-source areas, which are assumed to follow the source-scaling relationship and the omega-square source spectral model. We first estimated the strong motion generation area that reproduces near-source ground motions in a broadband frequency range of 0.3–10 Hz for the 2004 earthquake, by fitting the synthetic acceleration, velocity, and displacement waveforms to the observed data. The source properties of the obtained strong motion generation area are in agreement with the predictions made using an empirical source scaling relationship for crustal earthquakes, implying a stress drop of approximately 10 MPa for the 2004 earthquake. We then modeled the strong motion generation area for the 1977 damaging earthquake using the 2004 earthquake as an empirical Green’s function and constructing a source model based on its estimated source parameters. To simulate the unique record at Bucharest, capital city of Romania, the rupture was assumed to have propagated from the northeast bottom of the strong motion generation area having a stress drop of 50 MPa. Broadband ground motion simulations were further compared in terms of the modified Mercalli intensity values, calculated from the peak ground accelerations and peak ground velocities of synthetic waveforms, with the observed Medvedev–Sponheuer–Karnik intensity values. Our estimates of the source properties for the 2004 and 1977 Vrancea intermediate-depth earthquakes support the size-dependent stress drop.

Authors:
Poiată N., Miyake H., Koketsu K.

Abstract:
We analyzed the seismological aspects of the near-fault ground motion pulses and studied the main characteristics of the rupture configuration that contribute to the pulse generation for dip-slip faulting events by performing forward simulations in broadband and low-frequency ranges for different rupture scenarios of the 2009 L’Aquila, Italy (M w 6.3) earthquake. The rupture scenarios were based on the broadband source model determined by Poiata et al. (Geophys J Int 191:224–242, 2012). Our analyses demonstrated that ground motion pulses affect spectral characteristics of the observed ground motions at longer periods, generating significantly larger seismic demands on the structures than ordinary records. The results of the rupture scenario simulations revealed the rupture directivity effect, the radial rupture propagation toward the site, and the focusing effect as the main mechanisms of the near-fault ground motion pulse generation. The predominance of one of these mechanisms depends on the location of the site relative to the causative fault plane. The analysis also provides the main candidate mechanisms for the worst-case rupture scenarios of pulse generation for the city of L’Aquila and, more generally, the hanging-wall sites located above the area of large slip (strong motion generation area).

Authors:
Bălă A.

Abstract:

Authors:
Bălă A., Radulian M., Popescu E., Toma-Dănilă D.

Abstract:

Authors:
Constantin A. P., Moldovan I. A., Lavigne F., Grancher D., Partheniu R.

Abstract:
Tsunami is one of the major natural hazards presenting significant flood risk for coastal communities and therefore, increasing the society resilience to this phenomena in exposed areas is very important for minimizing damage and possible destructive effects on the environment in these areas. In the frame of the EC Programme-FP7 ASTARTE project (Assessment, Strategy And Risk reduction for Tsunamis in Europe), we conducted a questionnaire survey among people living, working, or visiting Eforie Nord site. The tsunami questionnaire has been translated in Romanian language, the questions referring to: interviewee's relation to Eforie Nord site, information about interviewed people, tsunami hazard knowledge/risk perception, evacuation issue, awareness of the existing warning system, information, and communication. The results obtained after the survey confirm that coastal communities from Romania are not resilient to tsunami hazard. Our respondents have mentioned from natural and anthropic types of hazards, the tsunami as third rank in Eforie Nord test site, coming after earthquakes and storms. Whatever the respondents status (i.e. local population, or tourists), earthquakes and sea withdrawal are cited as tsunami warning signs by 62% and 60% of the respondents, respectively. Regarding the perception of a future tsunami event in Eforie Nord, 36.3% of the respondents think that the place could be affected by a tsunami and the tsunami wave could reach more than 2-5 meters (heights cited by approx. 14% of respondents) or even more than 5-10 meters (values cited by 15% of interviewed people).

Authors:
Constantin A.P., Moldovan I.A., Partheniu R.

Abstract:
The goal of this paper is to present some observations about the abnormal animal behavior prior to and during some Romanian subcrustal earthquakes. The major Vrancea earthquakes of 4 March 1977 (MW = 7.4, Imax = IX–X MSK), 30 August 1986 (MW = 7.1, I0 = VIII–IX MSK) and 30 May 1990 (MW = 6.9, I0 = VIII MSK), were preceded by extensive occurrences of anomalous animal behavior. These data were collected immediately after the earthquakes from the affected areas. Some species of animals became excited, nervous and panicked before and during the earthquakes, such as: dogs (barking, howling and running in panic), cats, birds (hens, geese, turkey hens, ducks, pigeons, parrots), cattle, pigs, mice and rats (came into the houses and have lost their fear), horses, fishes, snakes etc. These strange manifestations of the animals were observed on the entire territory of the country, especially in the extra-Carpathian area. This unusual behavior was noticed within a few seconds to days before the seismic events, but for the most of cases the time of occurrence was within two hours prior to the quakes. We hope that one day the abnormal animal behavior will be documented enough in order to be used as a reliable seismic precursor for the intermediate depth earthquakes.

Authors:
Moldovan I.A., Grecu B, Constantin A.P., Anghel A., Manea E.F, Manea L., Partheniu R.

Abstract:
In the last decade, many efforts were done to predict the macroseismic intensity in case of felt Vrancea earthquakes and additionally an online environment was developed for the automatic approximation of the intensity from peoples’ feedback. Besides the extended scientific studies, the near real-time estimation of the macroseismic intensity recently became mandatory for the insurance companies to cover some of the losses and damages that earthquakes might cause to houses, belongings, and other structures. Due to the insurance companies’ requests, the macroseismic questionnaires method was doubled by the seismic intensity determination using instrumental data, as recommended in the Romanian Seismic Intensity Scale Standard (STAS 3684-71). In the present study, the procedure is shown, for the last earthquakes with ML larger than 5.0, occurred in Vrancea zone, and felt on the extra-Carpathian area. We have selected the case study in Barlad, Vaslui county, because there have been recorded the largest accelerations (122 cm/s2) and have been reported the largest MSK intensities (VI) from Romania during the Mw 5.5 September 24, 2016 earthquake. The results obtained using the two approaches (macroseismic and instrumental data) have been compared and some differences have been found.

Authors:
Moldovan I. A., Toader V. E., Moldovan A. S., Ghica D., Constantin A.P.

Abstract:
The atmospheric sound waves with frequencies lower than 20Hz are named infrasound waves. Among the multitude of infrasonic signals that have been recorded and detected during time, some of them have been associated with different natural or anthropogenic sources and the source of many other remaining hidden and unknown. At the beginning of year 2013, a permanent infrasound monitoring system composed by a MB AZEL2007 microbarometer, the digitizer and the transmitting equipment, was installed by NIEP, at Mangalia, Romania, on the Black Sea coast line (at 50m from the water front) to test the infrasonic method in correlation with local, regional, and global sources producing acoustic waves with frequencies lower than 20Hz. Five years of recordings show at lower frequencies (less than 2Hz) a predictable behavior of infrasonic activity on the seashore, suggesting the presence of highly coherent infrasound waves in atmosphere. At higher frequencies (2Hz-8Hz) there appeared a type of waves that was never recorded before by our infrasonic sensors in other locations far away from the sea shore. The interesting aspect on the spectrogram resides in well defined, visible superior harmonics of the dominant signal, which develops between 2 and 8Hz. These harmonics are clear and create the specific spider legs aspect present in spectrograms. The precise source of these high amplitude signals at higher frequencies is under investigation and a couple of suppositions have been made. One of them refers to the composition of atmosphere that might be possible to act as a band pass filter which selects certain preferred frequencies from the background infrasonic noise induced by water's surface. The propagation parameters of this filter may be altered by aerosols concentration, humidity, temperature and, perhaps, by other factors. The corroboration of the infrasound recordings and spectrograms with local meteorological data show a good correlation between the spectrogram and the daily variation of the humidity parameter.

Authors:
Moldovan, I.A., Toma-Dănilă D., Constantin A.P., Plăcintă A.O., Popescu E., Ghiță C., Diaconescu M., Moldoveanu T., Paerele C.M.

Abstract:
The most important specific requirements towards dams’ safety is the seismic risk assessment. This objective will be accomplished by rating the dams into seismic risk classes using the theory of Bureau and Ballentine, 2002, and Bureau (2003), taking into account the maximum expected peak ground motions at dams’ site, the structure's vulnerability and the downstream risk characteristics. The maximum expected values for ground motions at dams’ site have been obtained using probabilistic seismic hazard assessment approaches (PSHA) for dams situated on Bistrita and Siret Rivers and their tributaries. The structural vulnerability was obtained from dams’ characteristics (age, high, water volume) and the downstream risk was assessed taking into account human, economical, touristic, historic and cultural heritage from the areas that might be flooded in the case of a dam failure. The results of the work consist of local and regional seismic information, specific characteristics and locations of dams, seismic hazard values and risk classes, for all sites. The studies realized in this paper have as final goal to provide in the near future the local emergency services with warnings of a potential dam failure and ensuing flood as a result of a large earthquake occurrence, allowing further public training for evacuation.

Authors:
Moldovan I. A., Constantin A. P., Plăcintă A. O., Toma-Dănilă D., Ghiță C., Moldoveanu T., Paerele C. M.

Abstract:

Authors:
Partheniu R., Craiu A., Diaconescu M., Ioane D., Moldovan I.A.

Abstract:
Previous studies have shown that the Black Sea was subject to tsunami wave generation in the past (Altinok, 1999), with a total of twenty-two events generated. According to recent studies by Diaconescu et al. (2008), the Black Sea is divided into nine seismic sources. A more recent approach structures the area in ten different seismic sources, given by Moldovan et al. (2016, 2017). This study focuses mostly on the Istanbul seismic source, which triggered in the past high magnitude earthquakes followed by tsunami waves. The most recent event generated in the Black Sea was on 15th of October 2016, with a magnitude Mw =5.1, at a depth of 10 km, with the following location: Latitude 42.19° N, Longitude 30.68° E. The focal mechanism determined through the moment tensor inversion (U.S. Geological Survey – USGS) indicates a reverse faulting type. For this event, a few tsunami modeling scenarios were run. When using the exact parameters of the earthquake (Mw = 5.3), the simulations show no results. More simulations were computed, increasing the magnitude with steps of 0.2, from 7.0 up to 7.8. The modeling was accomplished using the Tsunami Analysis Tool (TAT), software provided by the Joint Research Center (JRC) from Ispra, Italy. The results of these tsunami simulations show low wave heights for a magnitude of 7.2, a of maximum 0.42 min Eregli (Turkey), 0.36 m in Zonguldak Eregli (Turkey), and 0.32 m in Kilimli (Turkey). For a magnitude of 7.6, the maximum wave heights are higher, considered to be moderate, of 1.59 m in Zonguldak Eregli(Turkey), and 1.21 m in Eregli (Turkey). Moreover, there are three locations from the Romanian shoreline affected, as follows: 0.83 m in Mangalia, 0.5 m in Techirghiol, and 0.39 m in Constanţa. In order to obtain a correlation of these simulations to real events of high magnitude, we will compare them with two past earthquakes from the Istanbul seismic area, generated on the 12th of November 1999 (Mw = 7.2) and 17th of August 1999 (Mw = 7.6). Due to their location inland, the results for these two earthquakes display very low wave heights, a of maximum 0.18 m. These events were also modeled using the same software, same methodology, considering as location an offshore position of the earthquakes, assumed as being generated on similar faults. The results were compared to the modeling output of the 2016 earthquake from October. For a better evaluation of the tsunami waves possibility of occurrence in the Istanbul seismic area, more information regarding the parameters of high-magnitude earthquakes, their location and focal mechanism type, are necessary.

Authors:
Partheniu R., Constantin A.P., Moldovan I. A., Ioane D., Grecu B.

Abstract:

Authors:
Rogozea M., Moldovan I.A., Constantin A.P., Manea E.F., Manea L.M., Neagoe C.

Abstract:
The Vrancea seismic region, located at the bending area of the South–Eastern Carpathians in Romania, is the most active zone of seismicity in Europe, producing earthquakes at intermediate depths (60–200 km). The major events (magnitude above 7) are generated at intermediate depth and produce specific patterns of damage over extended areas. In this study we test the macroseismic intensity attenuation laws, using the intensity data point (IDPs) for 8 intermediate depth earthquakes that occurred in Vrancea (between 1738 and 2000). The macroseismic attenuation laws used for testing were Moldovan (Metode si modele statistice in seismologie. Editura Morosan, Bucuresti, pag 236, 2007), Sorensen et al. (Soil Dyn Earthq Eng, 2010), Vacareanu et al. (Macroseismic intensity prediction earthquake for Vrancea intermediate-depth seismic source. Hazards, Nat, 2015). The main purpose of the testing is to determine the best attenuation law that will be used to estimate the expected macroseismic intensity at different sites, and to further use them in the assessment of the seismic hazard and risk of the country and to design the real time shake maps. In conclusion, we have decided that Moldovan (Metode si modele statistice in seismologie. Editura Morosan, Bucuresti, pag 236, 2007) is the best intensity attenuation law for earthquakes located around 90 km depth (the events from March 4, 1977 and May 30, 1990), Sørensen et al. (Soil Dyn Earthq Eng, 2010) law is the best for modelling the macroseismic field due to earthquakes from the lower segment, located around 130 km depth (events from November 10, 1940 and August 30, 1986). For epicentral distances larger than 300 km, Vacareanu et al. (Macroseismic intensity prediction earthquake for Vrancea intermediate-depth seismic source. Hazards, Nat, 2015) law fits best the intensity distribution.

Authors:
Bălă A., Tătaru D., Grecu B.,

Abstract:
Tectonic of Romania includes both pre-alpine platforms and Alpine orogenic structures. The pre-alpine platforms are: Eastern European Platform, with its western margin in Romania—Moldavian platform; Scythian platform; Moesian platform.

Authors:
Toader V.E., Moldovan I.A., Ionescu C., Mărmureanu A.

Abstract:

Authors:
Toma-Dănilă D., Cioflan C.O., Armaș I.

Abstract:
In this paper we highlight the capabilities and advantages of GIS, through an explicit analysis of its contribution within different studies of seismic hazard and risk assessment. These studies are related to Romania – one of Europe’s countries with the highest seismic risk, mainly due to intermediate-depth earthquakes originating in the Vrancea Zone. We provide examples of how GIS contributes and enhances the evaluation of seismic hazard, the development of vulnerability spatial datasets, multicriteria analysis, real-time estimation of seismic risk, assessment of road network failure susceptibility and implications, mapping or others. The role of free data and contribution capabilities are discussed. In recent projects such as Bigsees and Ro-Risk, GIS was one of the elements that lead to innovation, and we aim to present the experience and results. Another important aspect is referred to: the importance of GIS to a research dissemination with great impact.

Authors:
Oros E., Popa M., Diaconescu M.

Abstract:
The study region is the most important seismic region of Romania whenwe refer to the crustal seismicity as a source of seismic hazard. So far there havebeen recorded 91 seismic events that produced signi fi cant effect in buildings(Io > 6 EMS), some of them resulting in severe damage and even casualties(Io > 7 EMS). In this paper we modelled the seismogenic sources in the regionusing a new seismotectonic model constructed on new earthquakes and focalmechanisms catalogues basis. This model was elaborated starting from the rela-tionship between geology and historical and instrumental seismicity and then it wasbetter constrained by geophysical, neotectonic, geodetic data and particularly byactive stress fi eld features. The stress tensor parameters and the stress regime havebeen determined by formal inversion of the focal mechanisms solutions. Our studyprovides evidence of at least seven different deformation domains with different tectonic regimes as a realistic support for assessing the seismogenic potential of thegeological structures. Each seismogenic source is characterized by completenessmagnitude (Mcomp), maximum probable magnitude (Mmax) and magnitude — recurrence parameters. The probabilistic hazard maps produced in terms of PGAusing the new seismic sources highlights the importance of their con fi guration onthe hazard parameter values and their spatial distribution

Authors:
Țigănescu A.

Abstract:

Authors:
Năstase E., Muntean A., Ionescu C., Mocanu V., Ambrosius B.A.C.

Abstract:

Authors:
Apostol B.F., Bălan S.F., Bratoșin D.

Abstract:
The technique named "base isolation", resorts to place at the bottom of buildings special components, leading to long fundamental periods that would avoid resonance tendency of buildings with its site in the case of strong earthquakes. The nonlinear characteristics of the isolator layer change the linear period-shift estimation and can lead either to dangerous shortening shift in case of hardening nonlinearity or to unnecessary shift enlargement in case of softening nonlinearity. By neglecting this period-shift dispersion of the base isolation technology ? the drawing out of structure from dangerous resonant zone - can be compromised. The vulnerability of a structure to strong earthquakes can be appreciated by comparing its fundamental period with the fundamental period of soil deposit. Under high stresses the rocks became nonlinear dependent of their dynamic characteristics. Oscillating systems with non-linear behavior (as a consequence of materials) have multiple resonances. This behavior imposes a new assessment for period-shift due to nonlinearity. The dispersion of the natural periods with respect to the loading is an important factor. In the same time, the period-shift from a fixed-base to an isolated base of the same structure depends on the nonlinear characteristics of the isolator and site layers. By neglecting the nonlinear aspects, a base-isolated structure may be brought in resonant conditions even if the structural and isolated layer natural periods are different.

Authors:
Apostol B.F., Bălan S.F., Bratoșin D.

Abstract:
Maximum damage due to strong earthquakes occurs at the resonance between the natural periods of the structure and its site, given by the coincidence (or just close to) of the two periods, in which case the dynamic amplifications can damage, even destroy, the structure. From the recordings of (strong) Vrancea earthquakes one can see a dependence of the site natural periods and peak ground accelerations (PGA) on magnitude. For safe avoidance of the resonance it is necessary to define for each site a natural period value range corresponding to strong earthquakes. In the range of MGR=7- 7.5, which are considered as destructive magnitudes, with assigned PGA values of approximately ~0.1 to 0.3g and dangerous natural period range between 1.22 up to ~1.65s for INCERC site, the recommendation is to avoid buildings with these resonance characteristics. But for a large majority of sites only seismic recording of low and moderate events are available. The evaluation of the fundamental period for strong earthquakes using only seismic data implies an extrapolation procedure with inherent large errors. The resonant column determination by interpolation of the nonlinear variations in normalized form together with the determination of the normalization value T0 from seismic recording can lead to a better approximation of the natural periods for large PGA values. The paper shows ways of obtaining the site nonlinear natural period from in situ measurements, T0, and from resonant column data, Tn(PGA). With the help of normalized natural period functions Tn = Tn(PGA) we can predict natural period values of sites for strong earthquakes, starting from small and moderate seismic events, which gives us a good possibility in mitigation of seismic risk for future buildings.

Authors:
Constantinescu E. G., Diaconescu D., Grecu B.

Abstract:
This paper presents a basic description of the geological and tectonic setting of the areas of placement of four seismological observatories located in the eastern part of Romania. The four seismological observatories are MLR ? Red Mountain Seismologic Observatory, NEHR ? Nehoiu Mountain Seismological Observatory, ODBI ? Odobesti Seismological Observatory and VRI ? Vrancioaia Seismological Observatory. This observatories were chose because of their importance and proximity to the seismic active Vrancea region. Many geologic studies, of this areas, were carried out through time, resulting in a vast literature, studies, several geologic sections and maps. This descriptions were compiled from the geologic and tectonic maps, geologic sections, studies and literature, mentioned above, for every location of the observatories. For each one, of the sites, a geotectonic map was drawn, showing the main geologic formations and tectonic features. This geotectonic information was synthetized to add a better view to the lithological and tectonic history of each of the sites. Through this paper, we hope to provide clearer information and understanding of the geology and tectonics in which the mentioned observatories are set.

Authors:
Craiu A., Craiu M., Mihai M., Diaconescu M., Ghiță C.

Abstract:
Catalog of focal mechanisms for Vrancea (Romania) intermediate depth earthquakes (2005-2017)

Authors:
Craiu A., Dăneț A., Mihai M., Craiu M., Mărmureanu A.

Abstract:
One of the main objectives in real-time assessment of seismic hazard is the development of algorithms for rapid estimation of the seismic source parameters (fault planes solutions). The objective of this work is to test and implement new methodologies in the National Institute for Earth Physics (NIEP) for near real time estimation of fault planes solutions taking the advantage of the spatial density of the Seismic Network in seismically active zones ( 120 seismic stations used in real time) and the full range of tools used. To determine fault planes solutions was implemented the FPL code (code that generates parameters: strike, dip, rake, etc.) in ANTELOPE 5.6, software developed by Kinemetrics This code (FPL) uses the classic criteria to determine the focal mechanisms, namely P wave polarities, systematic tests of all possible fault plane solutions, so will validate only those solutions who met the required criteria. Another cod- Psmeca -is a code developed in GMT, which reads data values from files and generates PostScript code that will plot a focal mechanism on a map. These programs were implemented in the routine analysis ANTELOPE 5.6 software. Estimating the near-real-time fault planes solutions using dedicated programs, a few minutes after the event occurrence is done by generating locations of the seismic events with magnitude ML?4 for seismic events occurred at intermediate depths (H?60 km).

Authors:
Besuțiu L., Manea V.C., Pomeran M.

Abstract:
To avoid shortcomings of the current models attempting to explain genesis of the Vrancea intermediate-depth earthquakes the alternative model of an unstable triple junction (VTJ) had been previously proposed mainly based on a speculative approach. The paper deals with results of the latest research, including high-resolution seismic tomography obtained through the joint inversion of seismic and gravity data, and numerical modelling of the mantle convection that brings new evidence to support VTJ as a valid alternative for Vrancea intermediate-depth seismicity geodynamic setting. Of a special interest proved to be the advanced numerical modelling run on a High Performance Computing Cluster own by Solid Earth Dynamics Department in the Institute of Geodynamics of the Romanian Academy that has demonstrated how a stable triple lithospheric contact may transform into an unstable triple junction under the influence of a thermal anomaly even in the absence of differences between the plates velocities.

Authors:
Craiu M., Gallo A., Costa G., Dăneț A., Craiu A.

Abstract:
The seismicity of Romania is significantly affected by earthquakes produced by the Vrancea seismic source with intermediate depth events (3 shocks/century with magnitude Mw greater than 7.0). The seismic activity on the Romanian territory consists of both shallow and intermediate-depth earthquakes. The crustal seismicity is moderate and more scattered in comparison with the intermediate-depth one. The recent upgrade of the seismic network in Romania with high dynamic range accelerometers ( 114 real time seismic stations equipped with episensors) allows recording of moderate to large magnitude earthquakes at very close epicentral distances (less than 10-20 km). Strong motion data of high quality are also of help in increasing the effective preparation against seismic disasters, and the response during seismic emergencies. The consequent increased ability of a community to quickly recover from the damages of an earthquake thus contributes to lower the seismic risk, usually measured in term of casualties and economic losses. During 2016 in this seismic area were recorded two moderate events with 5.7 magnitude in September respectively December. The purpose of this work consists mainly in the estimation of moment magnitude Mw using the strong motion network of the NIEP. A stable and automatic method was developed by Gallo et al.,2014, has been implemented in the real time data acquisition and processing system (ANTELOPE) to estimate in real time the seismic moment, the moment magnitude and the corner frequency of events recorded by accelerometers, using Andrews (1986) method applied to S waves. The main goals are the independent estimation of seismic moment and the common characterization for all events recorded by the strong motion network.

Authors:
Diaconescu M., Craiu M.G., Oros E., Craiu A., Constantinescu E.G.

Abstract:
The paper highlights the seismicity of the Strei-Hateg depressionary system. This system is situated in the western part of the Southern Carpathians, and consists of two intermountain, post orogenic basins, Hateg basin and Strei basin. These two basins are separated by a threshold. The seismicity is characterized by moderate magnitude with a maximum magnitude of 4 (Mw) (8 September 2013) and by the presences of the seismic sequences. In the area are known two seismic sequences, one in 2011 of 14 earthquakes of 2 to 3.3 magnitude, main shock of 3.3 (Mw) and one in 2013 of 30 earthquakes with magnitude of 2 to 4 (Mw), main shock of 4 (Mw). The hypocentral depths are in 5 to 13 km depth interval with two exceptions, one earthquake with 19.6 km hypocentral depth (2013/09/08) and the other with 23.8 km hypocentral depth (2013/09/11). The sequence of March 2011 is a seismic swarm, with three shocks of 3.1, 3.2, 3.3 (Mw) and the other shocks between an interval of 1.9?2.4 (Mw). The sequence of September 2013 has an earthquake of magnitude 4.0(Mw) considered as a main shock. It was preceded by 9 foreshocks and followed by 25 aftershocks. The focal mechanisms of the earthquakes indicate a strike slip predominant movement with slight normal or inverse components.

Authors:
Ghiță C., Craiu A., Craiu M.G., Diaconescu M., Mărmureanu A.

Abstract:
The moderate-size earthquake with local magnitude 5,7 which occurred on November 22, 2014 in Vrancea region, at 41 km depth, is the largest crustal event instrumentally recorded at the bending of the Eastern Carpathians. Using the method developed by [2] termed the Hash method, (incorporated in Seisan software) we obtain the focal mechanisms for earthquakes that occurred in Vrancea region associated with the seismic sequence of November 22, 2014. We have examined the main shock and 29 aftershocks that occurred after 22 November 2014. P-wave arrivals and polarities are manually identified on the vertical component of each station. Polarities are marked as impulsive or emergent and the pick is given a quality rating (0- 4). We then use the S/P amplitude ratios computed from three?component seismograms, to determine mechanisms- Hash [2]. We had also investigate the spatial variation in focal mechanism type (e.g. strike-slip, normal, or thrust) and inferred fault strike. Most of the mechanisms are normal faulting, with the nodal planes oriented SE - NW, in agreement with the tectonic characteristics of the zone.This crustal seismicity is related to the normal fault system associated to Peceneaga - Camena major fault, which separates the Focsani Basin, part of the Moesian Platform, from the North Dobrogea promontory.

Authors:
Grecu B., Neagoe C., Partheniu R., Năstase E., Zaharia B.

Abstract:
In this paper, we analyze almost ten years of continuous recordings (November 2007? April 2017) from 114 stations of the Romanian Seismic Network using the power spectral densities and their corresponding probability density functions (PSD PDF). For each vertical station component, we compute the statistical mode for noise levels from the PSD PDFs. The noise mode represents the highest probability noise level for a given station. We then construct the PSD PDF mode low-noise model for Romania (RONM) from the minimum of all the noise modes at each period. The RONM is shown to be very close to the Peterson?s (1993) new low noise model. The diurnal and seasonal variations of the RONM are also shown. Finally, we compare our mode noise model with those obtained in similar way in different parts of the world: Greece, New Zealand and United States. We consider the RONM as a more realistic reference model for future installations of seismic stations in Romania and for assessing the performance of the existing ones.

Authors:
Grecu B., Toma-Dănilă D., Tătaru D., Ionescu C., Dăneț A.

Abstract:
Earthquakes represent a real threat in Romania. They can cause important damages, loss of lives, socio-economic as well as cultural losses. The National Institute for Earth Physics (NIEP) is the only governmental organization responsible for monitoring the seismic activity on Romania?s territory. NIEP provides different kind of information minutes to hours after the occurrence of a significant earthquake in Romania: near realtime information (location, depth and magnitude), ground shaking parameters and maps with the intensity of the shaking, post-event parameters, reports and macroseismic intensities. To issue such information, NIEP has been developing since 1980 one of the largest seismic networks in Europe, the Romanian Seismic Network (RSN). At present, RSN consists of 115 seismic stations equipped with velocity and accelerometer sensors and two seismic arrays. The increase of the density of the stations within RSN in the last decade led to a significant increase of the number of seismic events detected and located in Romania. RSN also provides valuable information for emergency managers in case of earthquake disaster, as it can provide rapid initial estimates and updated estimates of the location and extend of damage.

Authors:
Muntean A., Ambrosius B.A.C, Mocanu V., Năstase E.I., Ionescu C.

Abstract:
In this paper we present the results of an analysis of 15 years of continuous GNSS/GPS measurements in Romania. The purpose of this work is threefold: monitoring of crustal changes occurring in the Romanian territory in correlation with tectonic processes in South-East Europe (Africa-Europe plate interaction), observation of crustal movements in order to establish the surface-to-depth relationship of deep earthquakes in the area of the Eastern Carpathians bend zone (Vrancea region) and improving the accuracy of the coordinates of the national seismic network stations. The development of the Romanian GNSS/GPS (Global Navigation Satellite System/Global Positioning System) network started in 2001 when the first permanent station was installed at Lacauti in the Vrancea seismogenic area. Since then the network has grown to 27 stations covering the entire Romanian territory and is still expanding. In our analysis we also include 18 GNSS stations of the GeoPontica network, developed and maintained by the National Research and Development Institute for Marine Geology and Geoecology, with the purpose to monitor geodynamic processes in the Western Black Sea coastal area. It consists of 13 stations in Romania and 5 in Bulgaria. In this paper we provide a comprehensive description of the GPS networks, reflecting the actual capabilities, justifying implementation choices and presenting the results. The GPS data were processed in daily batches with the ?precise point positioning? (PPP) strategy using the GIPSY-OASIS software. From the resulting position timeseries the horizontal and vertical motion vectors were calculated relative to a stable Eurasian reference frame. The results of our study show that internally the Romanian territory appears to be quite stable, but the whole country trends to move slightly southward relative to Eurasia at velocity rates of about 2.5 ? 3.0 mm/yr, especially the southern part. We speculate that this is a far-field effect of slab roll-back due to the subduction of the African plate under the Eurasian plate at the Aegean trench, way to the south. Until now, we did not observe any long-term signals due to the deep Vrancea earthquakes because the effects on surface motion are probably small, but we will do more detailed studies of some recent (2016) Mw 5.3 seismic events in the Vrancea area.

Authors:
Neagoe C., Grecu B., Radulian M.

Abstract:
The focal mechanism and rupture directivity for intermediate-depth earthquakes occurred in the Vrancea source (Romania) are determined using FMNEAR algorithm [1]. The method is based on the waveform inversion of near-source seismic waveforms and on a linear finite source model. When the FMNEAR algorithm is started the first parameters that are determined are the moment magnitude (Mw), the double couple focal mechanism (strike, dip, rake) and the distribution of seismic moment along strike. This provides a first order estimate of rupture length and directivity. The depth of the source is also explored. A band-pass filter is automatically applied for each individual component of the recorded waveform (N, E, Z). The inversion is made in successive steps combining grid searches for (strike, dip, rake) parameters and simulation to determine rupture onset times and the shape of the local source time functions. Also a confidence index is defined. The method was tested on seismic events with magnitude higher than Mw = 3.5 recorded by the Romanian seismic network (broadband stations and accelerometers). Tests were made on events recorded by a large number of welldistributed stations and also for less favorable cases to evaluate the capability of the algorithm to constrain focal mechanism and source time function. In its present configuration, FMNEAR method is implemented in near real-time.

Authors:
Neagoe C., Grecu B., Manea L. M.

Abstract:
National Institute for Earth Physics (NIEP) has started the development of its own realtime seismic network since 2002. The network is designed to monitor the seismic activity on Romania territory, which is dominated by intermediate earthquake from the Vrancea area. In present the network consist of 115 seismic stations and two seismic array. The seismic stations are equipped with Quanterra Q330 or Basalt digitizers, broad-band seismometers (STS2, CMG40T, CMG 3ESP, CMG3T, PBB-200s) or shortperiod sensors (MARK L4C, MARK L22, RANGER). Most of the velocity sensors are collocated with Episensors Kinemetrics acceleration sensors. The processing software used by the National Data Center are Antelope and Seiscomp3. The program used for the automatic real-time locations in this study is Seiscomp3. Seedlink which is a part of Seiscomp3 is used for data acquisition in real time and also for data exchange. The automated software was tuned to obtain the most accurate location for the earthquakes and avoiding any false events. Different parameters were tested (like: STA/LTA, filters applied to the waveforms) on a data set of earthquakes representative for the local seismicity. Now Seiscomp3 is running in real time and detected over 300 seismic events. NIEP has developed a web application that uses the data stored in the database to display earthquake information, like location, magnitude and depth in real time. Another use for the data collected is to create and maintain contact lists to which datacenter sends notifications (email), based on the parameter of the earthquake. NIEP plans is to develop the means to cross-check the data generated between the different analysis systems. (e.g. comparing data generated by Antelope with data generated by Seiscomp).

Authors:
Oros E., Constantinescu E.G., Diaconescu M., Popa M.

Abstract:
The active stress pattern in the Apuseni Mts area is investigated and studied in relation to the local seismicity and geology. Our analysis is based on several high quality and resolution data bases obtained recently in the context of national and international projects and which refers to digital seismograms recorded by dense networks, parametric earthquakes catalogues and catalogues of focal mechanisms. The reduced stress tensor has been obtained by formal inversion of 89 focal mechanisms solutions. The maximum horizontal stress SHmax directions and tectonic regime change at local scale displaying a very heterogeneous stress field and claiming a major influence of local sources of stress. SHmax has systematic reorientations from NE-SW on the western border of the region to E-W in the South, NW-SE in the North and roughly N-S at the tectonic contact between orogenic structures with Transylvanian Depression. The stress and tectonic regimes show clear variations from a pure strike-slip in the structures of Pannonian Depression to extensions all over in the Apuseni Mountains, except the South Transylvanian Fault System area where an extensional strike-slip regime has been computed. The study area is characterized by a very low level of seismicity with a few scattered epicenters in the region or distributed in small clusters mainly on the borders where large neotectonic structures develop (grabens, faults). The study was completed with geodetic data and a seismotectonic model that brings new informations for understanding the seismic hazard and geodynamical processes in the study region.

Authors:
Rogozea M., Ghiță C., Radulian M., Glavcheva R., Toma-Dănilă D.

Abstract:
The Vrancea zone is an area of concentrated seismicity at intermediate depths (60-200 km) beneath the bending area of the South-Eastern Carpathians in Romania. The purpose of the paper is first to find historic data related to the four selected Vrancea earthquakes occurred on 26 November 1829 (Mw 7.3), 1 May 1893 (Mw 6.2), 17 August 1893 (Mw 7.1) and 31 August 1894 (Mw 7.1). Next, to gather all available historic information about those events, analyze it, assess/or convert the intensity using the Medvedev-Sponheuer-Karnik (MSK-64) scale. Further, to compile corresponding macroseismic maps for these earthquakes applying an optimized interpolation method (Kriging). The macroseismic effects distribution has been compared to the distribution of intensity in cases of instrumentally registered strong 20th century Vrancea events of 1940 (Mw 7.7), 1977 (Mw 7.4) and 1986 (Mw 7.1) in order to highlight possible correlation between the main earthquake parameters ? magnitude, source depth and macroseismic intensity

Authors:
Apostol B.F.

Abstract:
The notions of ‘elementary’ seismic sources and ‘elementary’ earthquakes are introduced, as being associated with ‘elementary’ tensorial point forces with a -like time dependence (where is the Dirac delta function). The tensorial character of these forces, known in Seismology as the dipole (or double-couple) representation, is given by the tensor of the seismic moment. A regular seismic source and a regular earthquake can be represented as a superposition of elementary sources and, respectively, elementary earthquakes, governed by a space-time structure factor of the seismic focal region. All these are new concepts. Elementary seismic sources are considered here for a homogeneous isotropic elastic half-space bounded by a free plane surface, the sources being located at an inner point in the half-space. A transient regime of generation and propagation of seismic waves is identified, as distinct from the stationary regime of elastic vibrations. This is another new concept. It is shown that elementary seismic sources produce (double-shock) spherical-shell waves (in the wave region), which are the well-known and waves associated with the feeble tremor in the recorded seismograms. Their mathematical expression, derived here from the tensorial force, differs from known, particular cases. These waves are called here collectively ‘primary’ waves. It is shown that the primary waves interact with the surface of the half-space, where they give rise to ‘secondary’ wave sources, placed on the surface. The secondary waves generated by the secondary sources (which may be called ‘surface seismic radiation’) are estimated here in a simplified model. It is shown that the secondary waves have a delay time in comparison with the primary waves and give rise to a main shock and a long seismic tail, in qualitative agreement with the seismic records. The secondary wave introduced here is a new concept; the main shock and its long tail derived here are elements of novelty. Similarly, the secondary waves generated by an internal discontinuity in the elastic properties of the half-space (an interface parallel with the free surface) are also estimated; it is shown that the discontinuity reduces appreciably the singular main shock on the free surface of the homogeneous half-space.

Authors:
Toader V.E., Moldovan I.A., Mărmureanu A., Ionescu C.

Abstract:
This paper describes the modalities of detection of events in a multidisciplinary network that monitor seismicity, telluric field, magnetic field, electric-electrostatic field, radio ULF waves, air ionization, radon concentration, solar radiation, infrasound, light and acoustic phenomena, meteorological parameters, air-earth temperatures, satellite data with application in seismic Vrancea area (bending zone of Carpathians mountains). The most part of data analysis is automatically done into a distributed structure. Methods used are general but the measured parameters have to be adapted to particularities of monitoring area. Vrancea is a complex zone characterized by intermediate depth earthquakes concentrated and distributed on several levels deep. Data acquisition is followed by their analysis (detection, effects evaluation) and automatic transmission of alerts to beneficiaries specialized in emergency situations (Inspectorate for Emergency Situations, organizations involved in managing special events). Network monitoring allows tracking of climate change and it sends information in real time.

Authors:
Toma-Dănilă D., Armaș I., Cioflan C.O.

Abstract:
The assessment of seismic risk for transportation networks is a difficult task, due to its complexity, hard to get detailed data, lack of methods with low uncertainties and difficulty of defining inter-relations. Through this paper we identify viable ways of analysing the seismic risk of transportation networks in Romania, considering the availability and characteristics of specific data, the possibilities of adapting external knowledge and recently developed methodologies. Until now there was no coherent and complex approach in Romania for this task, referring to the bigger picture. Therefore, we propose an integrative framework that incorporates GIS capabilities (like the ones provided by the ArcGIS Network Analyst Toolbox) and test it for Bucharest. This framework can provide answer to important questions, like “which are the critical segments of networks” or “what could the implications of connectivity loss be?” in case of an earthquake. The approach relies on using fragility functions for critical structures like bridges and tunnels, on empirical formulas for estimating damage level, traffic flow characteristics or connectivity analysis. Results are depicted through multiple performance indicators.

Authors:
Zaharia B., Grecu B., Tătaru D., Oros E.

Abstract:
We propose to investigate the local seismic events in the western part of Romania using data from the SCP experiment, a joint project between University of Leeds, UK and National Institute for Earth Physics, Romania (South Carpathian Project – SCP), using 33 broadband seismic stations autonomously that operated in the western part of the country and continuously recorded data for two years (2009-2011). The seismicity in this area is characterized by shallow activity of moderate magnitude (magnitude below 6) earthquakes with frequent multiple sequences. Tectonically, the region is divided into blocks and basins bordered by intra-crustal faults. The major structural features developed in the region are: the Pannonian Basin with a thin subsiding lithosphere (cca 60 km) and four Dacidic units (Inner Dacides (ID), Transilvanides (T), Middle Dacides (MD), Marginal Dacides (MaD) and Outer Dacides (OD)) with a thicker lithosphere (100 - 140 km), uplifted by recent orogeny. These structures outcrop in the mountain chains and extend westward under the sedimentary cover of the Pannonian Depression. The newest (Neotectonic) tectogeneses were extensional (syn-rift phase) and compressional (basin inversion) resulting in brittle structures: grabens and horsts, separated by NW-SE oriented faults, affecting both the basement and the sedimentary cover. Two Neogene NW-SE oriented major grabens developed at the basement level of the Pannonian Basin: Sannicolau Mare in the West and Caransebes in the East. These structures are extended in the mountains as small depressions, controlled by Neogene normal faults, with the basement lowered down to over 7 km (at Hungary - Romania border). We applied the Wadati method to estimate the Vp/Vs ratio and used it to retrieve a P-wave velocity model for the investigated region. For a better constraint of local seismic events locations, we used the derived P-wave velocity model to relocate all the events using Joint Hypocentral Determination (JHD) method.

Authors:
Aldea A., Radulian M.

Abstract:
The seismic activity in Romania is dominated by the earthquakes generated at intermediate depths (60÷180 km) in the Vrancea region, located at the bend of the South-Eastern Carpathians. The seismicity concentrates in a narrow high-velocity lithospheric volume embedded in the upper mantle. The rate of seismic moment per volume, ~ 0.8 x 1019 Nm/yr, is comparable to southern California (Wenzel et al., 1998). The event produced on 10th November 1940 (Mw = 7.7) was the largest instrumentally recorded earthquake in Romania, was felt in several other countries ( Bulgaria, Republic of Moldova, Ukraine, Russia, Greece, Turkey, Hungary, Yugoslavia, etc.) and produced victims and damage on a wide area beyond Romania’s borders. The large magnitude, the huge macroseismic field (with seismic intensities reaching X), the relatively large number of victims, altogether rank the Vrancea 1940 earthquake as one of the major European seismic events.

Authors:
Zaharia B., Șerbu F., Tătaru D., Grecu B., Năstase E.

Abstract:

Authors:
Apostol B.F.

Abstract:
The displacement caused in an isotropic elastic half-space by a point force localized on or beneath its surface is calculated here by a new method. These classical problems are known as Boussinesq and, respectively, Mindlin problems. The motivation for the present work resides in the fact that the original solutions involve some particular procedures, required by the complexity of the boundary conditions, which may limit their general application. The solutions presented here are obtained by including in a generalized Poisson equation the values of the function and its derivatives on the boundary, and by using in-plane Fourier transforms. This method is general and can be extended to other, similar problems.

Authors:
Apostol B.F.

Abstract:
The representation of a localized faulting seismic source is reformulated, without resorting to the mechanical torque interpretation of the seismic moment tensor. A volume seismic source is introduced by means of the pressure exerted in a small spherical cavity. The elastic waves equation with localized (point) sources is discussed in an isotropic half space bounded by a plane surface, including the boundary conditions. The near-field approximation is used to get the solution of a quasistatic deformation, and the transient regime of far-field propagating elastic waves is discussed for the (time-pulse) seismic sources introduced here. The far-field approximation (waves region) is also presented.

Authors:
Ardeleanu L., Neagoe C.

Abstract:
A primary objective of the national seismic network operated by the National Institute for Earth Physics of Bucharest is the monitoring of the seismic activity on the territory of Romania. As a result of a considerable effort carried out during the past years, mainly since 2008, the network consists at present of 118 permanent digital stations – 99 stations with real time data transmission and 19 offline stations – distributed over the whole territory of the country. The goal of this study is to evaluate the contribution of the on-line network stations to the monitoring of the local normal depth seismicity. During the period January 1, 2008 – June 30, 2013, 5933 events with depth < 60 km and local magnitude ML ≥ 1.2 – earthquakes and quarry blasts – have been localized within the Romanian borders, or in their immediate vicinity, using the data of the national network. To estimate the effectivity of the individual stations we take into consideration the fraction of events localized using the station records (compared to the total number of events of the catalogue, which occurred during the time of station operation), and the location of the station site with respect to the shallow depth seismic sources. The analysis provides a measure of the overall network performance regarding the monitoring of the local seismic activity, and allows us to quantify the value of the individual stations for the localization of the seismic events on the territory of Romania; this information is crucial for decisions regarding the effectiveness increasing and future development of the national network.

Authors:
Ardeleanu L., Neagoe C.

Abstract:
The seismic survey of the territory of Romania is mainly performed by the national seismic network operated by the National Institute for Earth Physics of Bucharest. After successive developments and upgrades, the network consists at present of 121 permanent stations equipped with high quality digital instruments – 102 real time and 19 off-line stations – which cover the whole territory of the country. The goal of this study is to evaluate the individual contribution of the real time seismic stations to the monitoring of the intermediate depth seismicity of the Vrancea region, the seismogenic zone which controls the seismic hazard at regional scale. During the period January 1, 2008 – June 1, 2013, 1468 subcrustal earthquakes (depth ≥ 60 km) with local magnitude ML ≥ 1.3 were localized at the bend of the Eastern Carpathians, using the records of the national network. The performance of each station is estimated by taking into consideration the fraction of events that are localized using the station records, compared to the total number of events of the catalogue, which occurred during the time of station operation. The location of the site and the recovery rate of reliable data are essential elements in the evaluation of the individual station effectiveness.

Authors:
Armaș I., Ionescu R., Gavris A., Toma-Dănilă D.

Abstract:
Measuring seismic vulnerability is a complex and valuable endeavor. It allows us to focus resources where they are critically needed. In this research a variety of data was used to identify the most vulnerable areas in Bucharest in case of an earthquake. Socio-economic data from censuses in 2002 and 2011 were used to generate an overall spatial vulnerability index, while other variables such as earthquake scenarios and distance to resilience-enhancing points in space (e.g., parks, fire stations, etc.) helped to fine-tune the analysis and offered a comprehensive picture of where vulnerability hotspots can be found in an urban environment. The top three most vulnerable hotspots are analyzed and two underlying reasons for their vulnerability are proposed and discussed in more detail: education and connectedness. We applied uncertainty and sensitivity analyses to assess the stability of the results for the vulnerability hotspots. The general outcome of the research is an increase in the overall socio-economic vulnerability in the city in spite of the upward economic trend in the period of time under analysis. Some key challenges about the origins of vulnerability are raised.

Authors:
Bălă A., Tătaru D., Grecu B., Răileanu V.

Abstract:
Moesian Platform is an old massif in the SE Europe bordered to the north and west by the South Carpathians, to the south by the Balkans, to the east by the Black Sea and to the NE by the North Dobrogean Orogen and Scythian Platform. In the Romanian sector, placed north of the Danube river topography of platform shows elevations of 100 - 200 m. Basement of the platform is divided by the Intramoesian Fault in two tectonic sectors, which are different both in age and in composition: the Wallachian sector to the west and the Dobrogean sector to the east. The Dobrogean sector of the patform is prolonged to the east until the Black Sea in the Central and Southern Dobrogea units. Two fault systems cross the platform: one major system is parallel to the Carpathians and accommodates the sinking of platform under Carpathian Orogen; the other fault system is relatively transverse to the first, separating a succession of fault blocks. Sedimentary cover has a variable thickness from a few hundred meters to 10 km or more in Focsani basin. The top of basement was mapped in the last decade using seismic and well data. The crust is thinner in the south and thicker in the north of the platform down to 40-45 km. Crustal investigation of the platform was accomplished in several stages, using in general active seismic investigations. Several large angle seismic crustal lines were recorded and interpreted in the 1970’ years in the E and W part of the Moesian Platform. After 1990 some near-vertical reflection seismic profiles were recorded in the process of oil and gas exploration. Two large angle regional refraction lines (Vrancea’99 and Vrancea2001), having 240 km and 400 km respectively in length, crossed a large part of the platform. New studies on crustal structure are based on the receiver functions method and surface wave inversion applied to the earthquake data. Data are provided by the broad band seismic stations. A preliminary interpretation of the Ps phases indicates depths of 35 km for Vrincioaia station, 33 km for Targusor (TIRR). Comparing the RF and refraction results is observed a slight underestimation of Moho in VRI (-3 km) using receiver function method. The new crustal data lead to review the old crustal models allow the geophysicist researchers to propose a new improved one. The new model comprises a more detailed topography of the surfaces of Moho and top of lower crust across of platform. The new crustal model provides as well a distribution of the mean P-wave velocities within the upper and lower crystalline crust in the whole platform. The new model displays mean P-wave velocities of 5.9-6.4 km/s in upper crystalline crust and 6.6-7.0 km/s in lower crust. The depth of Moho is variable from 30 km in S to 45 km in NE

Authors:
Bălă A., Tătaru D., Grecu B., Toma-Dănilă D.

Abstract:
As a result of the continuous development in the last ten years of the network of the permanent broadband stations in Romania, valuable data for seismicity and crustal structure studies is now available, especially for the western part. Complementary to this national dataset, maintained and developed in the National Institute for Earth Physics, new data emerged from temporary networks established during the joint projects with European partners in the last decades. Such a joint project between University of Leeds, UK and National Institute for Earth Physics, Romania (South Carpathian Project - SCP), deployed 33 broadband seismic stations autonomously operated in an area covering the western part of the country and which continuously provided data for two years (2009-2011). This project offered a good opportunity to study the crustal structure of western part of Romania. The receiver function technique and a joint inversion method of receiver function and Rayleigh wave dispersion are employed in order to derive the 2D seismic velocity models for several seismic station locations. The results show a thin crust for stations located in the eastern part of Pannonian Basin (28-30 km). The stations within the Southern Carpathians are characterized by crustal depths of about 31-36 km. In the Apuseni Mountains the Moho discontinuity is replace by a transition zone extended between 31 to 33 km depth. Models of the variation of the seismic velocity in depth are developed along 3 lines crossing the western part of Romania. On the first 2 lines the Moho limit is placed and it coincide generally with the isoline of seismic transverse velocity of about 3.75 km/s.

Authors:
Bălă A., Toma-Dănilă D.

Abstract:
Bucharest is among the European capitals most vulnerable to earthquakes. Although located at a relatively large epicentral distance (about 140–160 km) from Vrancea area, Bucharest has suffered much destruction and loss of life during great Vrancea earthquakes. In the last century, November 10th, 1940 earthquake (Mw = 7.7) caused the completely collapse of Carlton building located in the central city area, killing over 300 people, and many other high buildings were affected in capital city as in other cities closer to the epicenter. More than 1000 people were killed in a matter of minutes in all Romania during the earthquake, while city of Panciu was destroyed in 90–95 % proportion. This was the moment when the first alarm signal regarding the introducing of mandatory regulations in the seismic design of buildings came out. However, the recommendations made by the specialists were largely ignored by the authorities of the time, so that the next major earthquake of March 4, 1977 (Mw = 7.4) caused the biggest recorded disaster in the history of Bucharest The earthquake of 1977 caused only in Bucharest the collapse of 32 buildings, 8–12 floors high, while about 150 old buildings, with 4–6 floors were badly damaged. Most of the collapsed buildings were built between the 1920 and 1940, they did not benefit of the anti-seismic design. In the case of Bucharest the buildings have been previously damaged in the 1940 earthquake and during the bombardments in the World War II. Over 1500 people died and about 7500 were wounded, most of them in Bucharest City. The total cost of the damage amounted to more than 2 billion dollars, two thirds being related to the capital city only. The aim of the paper is to present aspects related to the consequences of the Vrancea 1940 and 1977 earthquakes, highlighting the differences between the two catastrophic events and their consequences. Therefore everything learned from the past should not be forgotten in order to insure that the next catastrophic event will find a better prepared society.

Authors:
Bălan S.F., Poncos V., Teleagă D., Toma S.A., Apostol B.F.

Abstract:

Authors:
Behr Y., Clinton J., Cauzzi C., Hauksson E., Jonsdottir K., Craiu M.G., Pinar A., Salichon J., Sokos E.

Abstract:
The feasibility of earthquake early warning (EEW) is now widely recognized. However, EEW systems that are in operation or under evaluation worldwide have significant variations and are usually operated independently of routine earthquake monitoring. We introduce a software that allows testing and evaluation of a well‐known EEW algorithm directly within a widely used earthquake monitoring software platform. In the long term, we envision this approach can lead to (1) an easier transition from prototype to production type EEW implementations, (2) a natural and seamless evolution from very fast EEW source parameter estimates with typically large uncertainties to more delayed but more precise estimates using more traditional analysis methods, and (3) the capability of seismic networks to evaluate the readiness of their network for EEW, and to implement EEW, without having to invest in and maintain separate, independent software systems. Using the Virtual Seismologist (VS), a popular EEW algorithm that has been tested in real time in California since 2008, we demonstrate how our approach can be realized within the widely used monitoring platform SeisComP3. Because this software suite is already in production at many seismic networks worldwide, we have been able to test the new VS implementation across a wide variety of tectonic settings and network infrastructures. Using mainly real‐time performance, we analyze over 3200 events with magnitudes between 2.0 and 6.8 and show that, for shallow crustal seismicity, 68% of the first VS magnitude estimates are within ±0.5 magnitude units of the final reported magnitude. We further demonstrate the very significant effect of data communication strategies on final alert times. Using a Monte Carlo simulation approach, we then model the best possible alert times for optimally configured EEW systems and show that, for events within the dense parts of each of the seven test networks, effective warnings could be issued for magnitudes as small as M 5.0.

Authors:
Alexandrescu M., Bălan F.S.

Abstract:
The paper aims to present the first scientific events organized by the Romanian Academy that marked the academic interests in our country to explain the Principle of d’Alembert. The protagonists of this approach (D. Pompei (years 1914–1943) and Șt. Hepites in 1914) were related to the presentation of d’ Alembert`s basic ideas expressed in his „Traité de Dynamique” published in 1743 in which the author does not explicitly for mulate the famous principle that would bear his name and did not use the notion of „force of inertia”. In these circumstances the explanation of the Principles of d’Alembert bearing a strong didactical character has not engaged a debate of ideas, as only target was the primary form of d’Alembert’s contribution to the reformulation of the fundamental law of classical mechanics that Newton had formulated a century before. Through its Mathematics Section, Academy of Sciences organ ized a symposium on December 15th 1945 in the Mechanics Laboratory of the University of Bucharest. Two communications were presented „Forces of inertia in the light of the principles of dynamics” and „The phenomenon of inertia”, first by D.Germani, and the second by C. Budeanu. V.Vâlcovici, at the end, as the ini tiator, organizer and host of the event was pleased to declare an identity of views of the two outstanding relevant previous speakers, expressed in different ways, and richly illustrated through examples from various technical fields, interpreted competently and with power of persuasion. The paper presents in detail all these scientific approaches in theoretical mechanics, in the early twentieth century.

Authors:
Borleanu F., Grecu B., Popa M., Radulian M.

Abstract:
During the last decade Romanian Seismic Network has been significantly improved. A total number of 114 3-C seismic stations and the 2 seismic arrays ensure a good coverage of seismically active regions. As a consequence, the detection threshold decreased allowing location with higher accuracy of low magnitude (ML ~1.0) seismic events. This led to a contamination of Romanian earthquakes catalog with artificial events occurred in different regions. The goal of the present study is to apply various discrimination methods like: spectral and amplitude ratio techniques, complexity factor evaluation and a multi-parameter discriminant on a data set characterized by lower magnitudes events recorded between 2011 and 2015. The selected data consists of small events occurred in the northern part of Romania in the neighborhood of Bucovina array (BURAR). The analysis was carried out on the waveforms recorded with a high signal to noise ratio using the vertical short period array components. Our results revealed that despite of some overlapping, these techniques show a good capacity to discriminate artificial by natural events for the study region.

Authors:
Cioflan C.O., Iancovici M.

Abstract:
This chapter includes papers that deal with the seismic evaluation and rehabilitation of existing buildings in Romania and neighboring countries- e.g. Republic of Moldova, using both fundamental and cutting-edge approaches.

Authors:
Cioflan C.O., Toma-Dănilă D., Manea E.F.

Abstract:
One of the strongest earthquake in Romania was the Vrancea earthquake on 10 November 1940, with moment magnitude 7.7 and depth of 150 km. This event caused significant losses over a wide territory, up to Iasi and Craiova cities. The number of casualties in Romania was around 593 dead and 1271 injured and 65,000 homes were destroyed. A major questions nowadays is: “What could the consequences of a similar earthquake be?”. Through this paper we try to provide insights, by relying on the newly implemented System for Estimating the Seismic Damage in Romania (SeisDaRo), operated by National Institute for Earth Physics (NIEP). This system uses the Improved-Displacement Capacity Analytical Method implemented in the SELENA Software for expressing building loss probabilities. The building database (at city or commune level) is classified into 48 types (depending on construction material, height and age), each with a specific capacity and fragility curve. For this paper we also compute casualty estimates. In the absence of real seismic recordings from the 1940 earthquake we obtained hazard parameters through different ground motion prediction equations (developed by Sokolov, Marmureanu or Vacareanu) specific for the Vrancea intermediate-depth source. Also we test the possibility of using data converted from intensity to acceleration. The damage estimates are represented on relevant maps. Our results show that an earthquake like the one on 1940 could lead to significant damage in our times.

Authors:
Clinton J., Zollo A., Mărmureanu A., Zulfikar C., Parolai S.

Abstract:
European researchers and seismic networks are active in developing new approaches to earthquake early warning (EEW), implementing and operating test EEW systems, and in some cases, offering operational EEW to end users. We present the key recent developments in EEW research in Europe, describe the networks and regions where EEW is currently in testing or development, and highlight the two systems in Turkey and Romania that currently provide operational systems to a limited set of end users.

Authors:
Constantin A.P., Moldovan I.A., Craiu A., Radulian M., Ionescu C.

Abstract:
On November 22, 2014 at 21:14:17 local hour (19:14:17 GMT) a ML=5.7 crustal earthquake occurred in the area of Marasesti city of Vrancea county (Romania) - the epicenter was located at north latitude 45.87° and east longitude 27.16°, with a focal depth of 39 km. This earthquake is the main shock of a sequence that started with this and lasted until the end of January. During the sequence, characterized by the absence of foreshocks, a number of 75 earthquakes were recorded in 72 hours, the largest of which occurred in the same day with the main shock, at 22:30 (ML= 3.1). The crustal seismicity of Vrancea seismogenic region is characterized by moderate earthquakes with magnitudes that have not exceeded MW 5.9, this value being assigned to an earthquake that occurred in historical times on March 1, 1894 (Romplus catalogue). Immediately after the 2014 earthquake occurrence, the National Institute for Earth Physics (NIEP) sent macroseismic questionnaires in all affected areas, in order to define the macroseismic field of ground shaking. According to macroseismic questionnaires survey, the intensity of epicentral area reached VI MSK, and the seismic event was felt in all the extra-Carpathian area. This earthquake caused general panic and minor to moderate damage to the buildings in the epicentral area and the northeast part of country. The main purpose of this paper is to present the macroseismic map of the earthquake based on the MSK-64 intensity scale.

Authors:
Constantin A.P., Partheniu R., Moldovan I.A.

Abstract:
Between years 2001 and 2004 a number of earthquakes with magnitudes which ranged from 3.9 to 5.0 occurred in the most seismically active areas of the Romanian territory. A macroseismic analysis of the effects produced on the Romanian territory has been conducted for these earthquakes, by using macroseismic questionnaires. Some of the observed intensities were significantly higher than those we could have expected after the earthquakes with such magnitudes. Effects have been evaluated from macroseismic observations giving maximum intensities estimated as VI–VII and VII in the MSK scale, respectively. Given the small to moderate size of earthquakes, many of the observed damages to buildings are due to their bad state, age, and poorly built without antiseismic protection, and hence particularly vulnerable.

Authors:
Craiu A., Diaconescu M., Craiu M.G., Mărmureanu A., Ardeleanu L.

Abstract:

Authors:
Craiu A., Diaconescu M., Craiu M.G., Mărmureanu A., Ionescu C.

Abstract:
The goal of this study is to analyze the seismic activity of the Vrancea intermediate depth source zone during the period 2010–2015, time interval when the data provided by the National Seismic Network reached high quantitative and qualitative levels. The Vrancea undercrustal source (60–200 km depth) is located in a small focal volume at the Carpathian Bend, and it dominates the seismicity of Romania. The data set consists of 1603 earthquakes with local magnitudes 1.8 ≤ ML ≤ 5.5, recorded between January 2010 and October 2015. The events were localized using ANTELOPE software for data acquisition and processing. The reliable P-wave polarities were used to estimate the focal mechanism of 80 earthquakes with ML ≥ 3.8.

Authors:
Craiu M.G., Craiu A., Mărmureanu A.

Abstract:
The seismic activity on the Romanian territory consists of both crustal and intermediate-depth earthquakes. The crustal seismicity is moderate and more scattered compared to the intermediate-depth one. In this paper we study the problem of homogeneous determination of local magnitude for earthquakes from the main seismic zones of Romania (Vrancea, Fagaras Mountains, Banat, Transylvania, Dobrogea and Romanian Plain). A waveforms database of digitally recorded data is used to derive new magnitude relations for different seismic areas of Romania. WoodAnderson amplitudes are computed from the available data and the maximum peak-to-peak amplitudes are measured on the horizontal components of the broad-band sensors to define the local magnitude scale. The duration magnitude (MD) is used as reference to calibrate the new magnitude scale based on amplitudes. The new coefficients are estimated through a multiple regression method. Our tests show that the new magnitude scale significantly improves the earthquake size evaluation and stability compared to the solution computed by present-day procedures at the National Institute for Earth Physics.

Authors:
Craiu M.G., Gallo A., Costa G., Mărmureanu A., Craiu A.

Abstract:

Authors:
Apostol A., Moldoveanu T., Sarlea A., Toader V.E.

Abstract:

Authors:
Diaconescu M., Craiu A., Toma-Dănilă D., Craiu M.G.

Abstract:
The study area is located at the contact between the Apuseni Mountains (Western Carpathians) with Pannonian Depression-to the west and with Transylvanian Depression - to the east. The eastern limit is marked by the Eastern Carpathians. The current tectonic activity is manifested by an uplift of the Carpathian Orogeny in relation to neighboring units, particularly the Pannonian Depression. The main seismological active areas are on the edge of the Pannonian Basin and in contact with the basement of Apuseni Mountains and Eastern Carpathians. Historical data suggests two potential earthquake magnitudes Mw >6, one of magnitude 6.2 (Mw) and one with magnitude 6 (Mw). Generally, the characteristics earthquakes of the area have magnitude Mw≤5.6. We expect that the horizontal components of the movement (generated by the uplift of the Carpathians) to produce a compressive stress, as shown by focal mechanism solutions.

Authors:
Diaconescu M., Craiu M.G., Craiu A.

Abstract:
In the present paper, we highlighted the two active seismogenetic zones, one of them to the north–east of Campulung city, and the other one along Ialomita River (west from Sinaia). Schematically we can say that the Southern Carpathians, between the Dambovita and Olt Valleys, are represented by the Supragetic Nappe, which has been over thrust on the Getic nappe during Middle Cretaceous. The Moesian Platform represents a Precambrian block involved in the Epihercynian European Platforms and is composed by three different segments, bounded by the Intramoesian and Calimanesti-Tg. Jiu crustal faults, the Dobrudjean, the Valachian and Danubian domains respectively. The Eastern Carpathians represent the central part of the Outer Carpathians belt and stretch from North to the junction with the Southern Carpathians along Intramoesian Fault. In the studied areal we covered all these units mentioned above and the main faults which mark the areal are Intramoesian Fault(IF) and Calimanesti-Tirgu Jiu fault, also there are a number of the medium to high angle reverse faults, thrust faults and strike slip to transpressional fault zones having a NW-SE direction. More of the earthquakes are located around six major seismogentic areas, such as: Campulung city, Sinaia city, Ialomita River, Targului Valley, Arges Valley and a W to E seismological line in Fagaras mountains.

Authors:
Ghica D.V., Grecu B., Popa M., Radulian M.

Abstract:
In order to discriminate between quarry blasts and earthquakes observed in the Dobrogea seismogenic region, a seismo-acoustic analysis was performed on 520 events listed in the updated Romanian seismic catalogue from January 2011 to December 2012. During this time interval, 104 seismo-acoustic events observed from a distance between 110 and 230 km and backazimuth interval of 110–160° from the IPLOR infrasound array were identified as explosions by associating with infrasonic signals. WinPMCC software for interactive analysis was applied to detect and characterize infrasonic signals in terms of backazimuth, speed and frequency content. The measured and expected values of both backazimuths and arrival times for the study events were compared in order to identify the sources of infrasound. Two predominant directions for seismo-acoustic sources’ aligning were observed, corresponding to the northern and central parts of Dobrogea, and these directions are further considered as references in the process of discriminating explosions from earthquakes. A predominance of high-frequency detections (above 1 Hz) is also observed in the infrasound data. The strong influence of seasonally dependent stratospheric winds on the IPLOR detection capability limits the efficiency of the discrimination procedure, as proposed by this study.

Authors:
Grecu B., Borleanu F., Tătaru D., Zaharia B., Neagoe C.

Abstract:
The characteristics of the background seismic noise recorded at a temporary seismic network have been analyzed using power spectral density estimates and their corresponding probability density functions (PDFs). The network was installed in Bucharest area for 10 months, between November 2003 and August 2004, and consisted of 32 seismic stations equipped with broadband velocity sensors. We investigated the noise level variations as a function of time of day and season. At high frequencies (> 1 Hz), seismic noise shows important diurnal variations for most of the stations, while in the microseismic domain (0.05 – 0.5 Hz) the noise level increases during the colder months of the year. A new approach to compute the horizontal to vertical (H/V) ratios and identify the resonant frequencies was introduced too. The H/V ratios determined from the median of the PDF show similar results, in terms of resonant frequencies, with those obtained when using noise data to compute the spectral ratios. Two resonant peaks, one with larger amplitude and one with smaller amplitude, were identified in the frequency bands 0.13 – 0.3 Hz and 0.5 – 0.9 Hz, respectively.

Authors:
Luzi L., Puglia R., Russo E., D'Amico M., Felicetta C., Pacor F., Lanzano G., Ceken U., Clinton J., Costa G., Duni L., Farzanegan E., Gueguen P., Ionescu C., Kalogeras I., Ozener H., Pesaresi D., Sleeman R., Strollo A., Zare M.

Abstract:
This article describes the Engineering Strong‐Motion Database (ESM), developed in the framework of the European project Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation (NERA, see Data and Resources). ESM is specifically designed to provide end users only with quality‐checked, uniformly processed strong‐motion data and relevant parameters and has done so since 1969 in the Euro‐Mediterranean region. The database was designed for a large variety of stakeholders (expert seismologists, earthquake engineers, students, and professionals) with a user‐friendly and straightforward web interface. Users can access earthquake and station information and download waveforms of events with magnitude≥4.0 (unprocessed and processed acceleration, velocity, and displacement, and acceleration and displacement response spectra at 5% damping). Specific tools are also available to users to process strong‐motion data and select ground‐motion suites for code‐based seismic structural analyses.

Authors:
Manea E.F., Michel C., Poggi V., Fah D., Radulian M., Bălan F.S.

Abstract:
Large earthquakes from the intermediate-depth Vrancea seismic zone are known to produce in Bucharest ground motion characterized by predominant long periods. This phenomenon has been interpreted as the combined effect of both seismic source properties and site response of the large sedimentary basin. The thickness of the unconsolidated Quaternary deposits beneath the city is more than 200 m, the total depth of sediments is more than 1000 m. Complex basin geometry and the low seismic wave velocities of the sediments are primarily responsible for the large amplification and long duration experienced during earthquakes. For a better understanding of the geological structure under Bucharest, a number of investigations using non-invasive methods have been carried out. With the goal to analyse and extract the polarization and dispersion characteristics of the surface waves, ambient vibrations and low-magnitude earthquakes have been investigated using single station and array techniques. Love and Rayleigh dispersion curves (including higher modes), Rayleigh waves ellipticity and SH-wave fundamental frequency of resonance (f0SH) have been inverted simultaneously to estimate the shear wave velocity structure under Bucharest down to a depth of about 8 km. Information from existing borehole logs was used as prior to reduce the non-uniqueness of the inversion and to constrain the shallow part of the velocity model (<300 m). In this study, we use data from a 35-km diameter array (the URS experiment) installed by the National Institute for Earth Physics and by the Karlsruhe Institute of Technology during 10 months in the period 2003–2004. The array consisted of 32 three-component seismological stations, deployed in the urban area of Bucharest and adjacent zones. The large size of the array and the broad-band nature of the available sensors gave us the possibility to characterize the surface wave dispersion at very low frequencies (0.05–1 Hz) using frequency–wavenumber techniques. This is essential to explore and resolve the deeper portions of the basin. The horizontal to vertical spectral ratio (H/V) curves provide important additional information about the structure and are here characterized by two major peaks. The first is attributed to the fundamental frequency of the basin, while the second can be interpreted as a mixture of the second higher mode of Rayleigh waves and other types of waves such as SH waves. This hypothesis has been verified by comparing the H/V curves with the SH-wave transfer function from the retrieved velocity structure. We could also approximate the SH transfer function with H/V ratios of earthquake recordings, providing additional verification of the robustness of the proposed velocity model. The Cretaceous bedrock depth was then inverted at each URS station from the fundamental frequency of resonance and using this model. A 3-D geophysical model for Bucharest has been constructed based on the integration of the inverted velocity profiles and the available geological information using a geographic information system.

Authors:
Mărmureanu G., Cioflan C.O., Mărmureanu A., Manea E.F.

Abstract:
Vrancea earthquake on November 10th, 1940 (MW = 7.7; MGR = 7.5; h = 150 km; E = 1.122 × 1023 ergs, Imax = IX½) represents the first large earthquake in the last century and was preceded by other earthquakes as: October 22, 1940 (MW = 6.5) and November 8, 1940 (MW = 5.9). If recorded, it would be given the opportunity to get basic data for seismic hazard assessment and useful conclusions for seismic design of structures to strong earthquakes. Unfortunately, no seismic ground motion was recorded and, as a consequence, no improvements of the Romanian design building code were made after this earthquake. The earthquake of November 10, 1940 confirms the existence of deep earthquakes in Vrancea area, deeper than Moho discontinuity in the lower lithosphere, and this theory was developed for the first time by H. Jeffreys in 1935. Focşani city and several municipalities (Coteşti, Panciu etc.) were almost destroyed and the houses not taller than one floor, were completely damaged. More than 45 churches and monasteries were damages, destroyed or demolished. New data regarding damages at monasteries have been synthesized and analyzed, the resulting intensities are completing the known macroseismic field and data may be used to construct the isoseismic map of the maximum possible Vrancea earthquake.

Authors:
Mărmureanu G., Mărmureanu A., Manea E.F., Toma-Dănilă D., Vlad M.

Abstract:
Seismic hazard is quantified by three parameters: level of severity, and spatial and temporal measurements. Thus, the purpose of a seismic hazard assessment is to determine these three parameters from instrumental, historical and geological observations. The characterization of earthquake ground motion for engineering applications generally involves the use of empirical models referred to as groundmotion prediction equations (GMPEs). In classic seismic hazard analysis, this GMPE describes a relationship between a ground motion parameter Y (PGA, PGV, MMI) in site, earthquake magnitude M, source-site distance R, and uncertainty or residual δ. Nothing on epicenter ground acceleration (PGA), velocity (PGV), MMI intensity. Selection of a ground motion for engineering design and other considerations requires a clear understanding of seismic hazard among stakeholders, seismologists and engineers in particular. The authors are coming with data in connection to strong and deep Vrancea earthquakes, the large uncertainties of peak ground accelerations (PGA) recorded in epicenter and far of epicenter in extra-Carpathian area after last three strong earthquakes (August 30,1986; MW = 7.1; h = 131.4 km; May 30,1990; MW = = 6.9; h = 90.9 km; May 31,1990; MW = 6.4; h = 86.9 km). There are many PGA records in Romanian and Republic of Moldavia seismic stations. Many of them are larger than in epicenter Vrâncioaia seismic station. Consequently, classic seismic hazard analysis is not applicable at all to strong and deep Vrancea earthquakes.

Authors:
Moldovan I.A., Diaconescu M., Popescu E., Radulian M., Toma-Dănilă D., Constantin A.P., Plăcintă A.O.

Abstract:
In this study we have used the most reliable and homogeneous seismic datasets at the European scale, covering historical and modern instrumental seismicity until present days for the Eastern part of Romania and the Black Sea Area for computing the statistical parameters of seimogenic sources and assessing the probabilistic hazard in the South Eastern part of Romania

Authors:
Armaș I., Toma-Dănilă D., Ionescu R., Gavriș A.

Abstract:
In this research, we calculate the probability and scale of population losses that may occur due to earthquake hazard in Bucharest. Losses are quantified in direct relation to the social vulnerability of people who are exposed to an earthquake event. Social vulnerability is based on index construction, using spatial decision rules to assess weights in a criteria tree using the SMCE-module of Ilwis software. To estimate building vulnerability, we used the Improved Displacement Coefficient analytical method in the SELENA software. For the earthquake loss estimation, we used the percentage of severely damageable residential buildings in each census unit (CU). The population loss estimation for the selected earthquake scenarios was obtained by multiplying the complex social vulnerability index with the estimated ratio of severely damageable buildings, for three selected earthquake scenarios and using the population numbers in each census unit. The maps represent the maximum affected population values, per census unit, in percentages. We provide useful estimates of the scale and severity of injuries, and link these with current levels of medical preparedness. In all scenarios, the CUs forming the Rahova neighbourhood revealed high loss values, due to significant problems in terms of the built environment and social vulnerability.

Authors:
Muntean A., Mocanu V., Ambrosius B.A.C.

Abstract:
The Petrosani basin is a large and important coal mining zone in the South Carpathians area of Romania. In recent times, most mines have been closed, but an extensive and dense network of galleries still exists. Most of the abandoned ones were not filled in with mine tailings. There is strong concern and evidence that the old galleries are collapsing and/or filling up with water, leading to significant surface deformation and potential hazards, especially for the local communities. We present an analysis of GPS data from nineteen (19) campaign sites spanning the period 2007–2012. Our results are quite consistent and show significant horizontal and vertical surface motions. The horizontal velocities range from 0 to 260 mm/year (mainly in WSW direction), while the vertical velocities range from +39 (uplift) to −263 (subsidence) mm/year. The largest motions appear to be associated with the central (oldest) sector of the mining area. The pattern of vertical motions suggests that the peripheral area is affected by slight uplift in response to the subsidence of the central sector.

Authors:
Năstase E., Muntean A., Ionescu C., Mocanu V., Ambrosius B.A.C.

Abstract:

Authors:
Năstase E., Muntean A., Toma-Dănilă D., Mocanu V., Ionescu C.

Abstract:

Authors:
Năstase E., Oikonomou C., Toma-Dănilă D., Haralambous H., Muntean A., Moldovan I.A.

Abstract:
We examine the lithosphere-atmosphere-ionosphere interaction with respect to earthquake events using Total Electron Content (TEC) data deriving from the Romanian permanent GPS network by applying three different techniques: a) estimation of TEC deviations from the mean state, b) Cross-Correlation Analysis and c) Spectral Analysis. The analysis concerns four seismic events that took place in Romania with magnitude ranging from 5.2 to 6.0. The aim is to identify and study possible ionospheric precursory phenomena linked to these seismic events.

Authors:
Neagoe C., Grecu B., Manea L.M.

Abstract:

Authors:
Daniel Paulescu, Maria Rogozea, Mihaela Popa, Mircea Radulian

Abstract:
The aim of this paper is to describe a managing system for a unique Romanian database of historical seismograms and complementary documentation (metadata) and its dissemination and analysis procedure. For this study, 5188 historical seismograms recorded between 1903 and 1957 by the Romanian seismological observatories (Bucharest-Filaret, Focşani, Bacău, Vrincioaia, Câmpulung-Muscel, Iaşi) were used. In order to reconsider the historical instrumental data, the analog seismograms are converted to digital images and digital waveforms (digitization/ vectorialisation). First, we applied a careful scanning procedure of the seismograms and related material (seismic bulletins, station books, etc.). In a next step, the high resolution scanned seismograms will be processed to obtain the digital/numeric waveforms. We used a Colortrac Smartlf Cx40 scanner which provides images in TIFF or JPG format. For digitization the algorithm Teseo2 developed by the National Institute of Geophysics and Volcanology in Rome (Italy), within the framework of the SISMOS Project, will be used.

Authors:
Pavel F., Văcăreanu R., Douglas J., Radulian M., Cioflan C., Bărbat A.

Abstract:
The probabilistic seismic hazard analysis for Romania is revisited within the framework of the BIGSEES national research project (http://infp.infp.ro/bigsees/default.htm) financed by the Romanian Ministry of Education and Scientific Research in the period 2012–2016. The scope of this project is to provide a refined description of the seismic action for Romanian sites according to the requirements of Eurocode 8. To this aim, the seismicity of all the sources influencing the Romanian territory is updated based on new data acquired in recent years. The ground-motion models used in the analysis, as well as their corresponding weights, are selected based on the results from several recent papers also published within the framework of the BIGSEES project. The seismic hazard analysis for Romania performed in this study are based on the traditional Cornell-McGuire approach. Finally, the results are discussed and compared with the values obtained in the recently completed SHARE research project. The BIGSEES and SHARE results are not directly comparable since the considered soil conditions are different—actual soil classes for BIGSEES and rock for SHARE. Nevertheless, the analyses of the seismic hazard results for 200 sites in Romania reveal considerable differences between the seismic hazard levels obtained in the present study and the SHARE results and point out the need for further analyses and thorough discussions related to the two seismic hazard models, especially in the light of a possible future harmonized hazard map for Europe.

Authors:
Plăcintă A.O., Popescu E., Borleanu F., Radulian M., Popa M.

Abstract:
The crustal seismicity in Romania is concentrated in front of the Carpathians Arc bend (Vrancea region) and at the contact between the extra-Carpathian platform regions and Carpathians orogen. The region investigated in this paper is characterizing the contact of the western side of the South Carpathians with the Tisza-Dacia region. In this area, the large amount of transcurrent deformation that took place during the right-lateral movement of the South Carpathians in respect to the stable Moesian unit let to the creation of intra-mountainous pull-apart basins able to accommodate this movement. For two such basins, Ha?eg and Caransebe?-Mehadia, recent good quality seismic data have recorded during three earthquake sequences: (1) a sequence of 14 events occurred on 24?31 March 2011 in the Ha?eg Depression (maximum magnitude of Mw = 3.3), (2) a sequence of 35 events occurred on 8?11 September 2013 in the Ha?eg Depression (maximum magnitude of Mw = 4.0) and (3) a sequence of 60 events occurred in the Caransebe?-Mehadia Depression on 31 October?15 December 2014 (main shock magnitude of Mw = 4.1). We apply empirical Green?s functions deconvolution and spectral ratios techniques to determine the source parameters. Despite the relative small size of the events, high-quality waveforms for pairs of co-located events are available in different measuring sites. The new results, together with previous determinations, provide a useful database to investigate the source scaling properties in correlation with seismotectonics modeling of the study region. Finally, source characteristics (location, seismic moment, source dimension, stress drop, focal mechanism, clustering) are discussed in connection with the seismotectonics features at the scale of the entire Carpathians and adjacent extra-Carpathians contact areas.

Authors:
Popa M., Oros E., Dinu C., Radulian M., Borleanu F., Rogozea M., Munteanu I., Neagoe C.

Abstract:
An earthquake swarm of 940 events with ML magnitude between 0.1 and 4.0 and the depth no more than 25 km occurred during three months in the South-Eastern Carpathians foredeep, in an area of around 200 km2, at 27 km north-east of the Galati city. JHD relocation highlights a rupture area steeply dipping down to 15 km depth along a NE-SW alignment. Although the area is known as seismically active, it was for the first time that such a massive sequence was recorded. Specific seismicity alignments and stress field patterns are emphasized and interpreted in terms of geotectonical features of the region. The analysis of the stress associated with the seismic swarm shows a predominant EW compression and NS extension which is compatible with the regional stress regime in the Carpathians foredeep area. The rather small b-slope value of the frequency-magnitude distribution (0.743) for the swarm events in contrast with the value characterizing the regional seismicity (1.890) suggests a significant increase in the local stress accumulation on relatively larger tectonic structures and is in favor of a major tectonic component of the mechanism responsible for generating the swarm.

Authors:
Popa M., Pavel F.

Abstract:
The papers contained in Part II of this volume are devoted to three main subjects, namely: seismicity of Romania, seismic hazard assessment and the evaluation of local soil conditions. A total of 11 papers authored by researchers from several institutions in Romania, as well as from Bulgaria and which cover all the three above-mentioned subjects were accepted for publication and are contained in this chapter. Some very brief abstracts of these papers are given below.

Authors:
Diaconescu M., Oros E., Craiu A.

Abstract:

Authors:
Popescu E., Radulian M., Plăcintă A.O.

Abstract:
The Vrancea seismic nest is a distinctive case of unusually clustered seismicity at intermediate depths. The source scaling properties are essential elements to understand and model the tectonic processes responsible for generating earthquakes in such a confined lithospheric volume. The purpose of the present paper is to investigate the scaling laws for Vrancea earthquakes on the basis of well-defined source parameters. Spectral ratios technique and empirical Green’s function deconvolution are applied to retrieve source parameters. Previous results are combined with new determinations resulting in an enlarged database (298 events), spanning a magnitude interval from Mw ~ 2.4 to Mw ~ 7.7 (1940 major event). The results show for the most of moderate-magnitude earthquakes a relatively simple source time function and source spectrum, compatible with a circular source model with homogeneous rupture process. The scaling of seismic moment with source radius and stress drop appears to be self-similar over the entire magnitude range of the considered data set (3.0 ≤ Mw ≤ 7.7) and matches well the theoretical scaling for source models generally adopted in source studies. Particular high stress drop values, for moderate and large events, indicate fast and efficient rupture processes at different scales, possibly explained by fast running shear melting processes.

Authors:
Rogozea M., Glavcheva R., Radulian M.

Abstract:

Authors:
Rogozea M., Radulian M.

Abstract:

Authors:
Rogozea M., Radulian M., Popa M., Paulescu D., Oros E., Neagoe C.

Abstract:
The macroseismic effects of three major events recorded in historical time (1738, 1802, 1838) are re-evaluated and compared with three major events recorded in the 20th century in the Vrancea subcrustal source (1940, 1977, 1986). The purpose of the paper is to detect characteristic resemblances and differences in the macroseismic distributions among the study earthquakes. They provide important clues in assessing focal depth interval and specific directivity effects of the sources produced in historical times. Certainly, extension of such information to historical earthquakes will contribute essentially to improve the reliability of seismic hazard evaluation.

Authors:
Stancu I., Ghica D., Radulian M.

Abstract:
The Infrasound Ploştina Array (IPLOR) is part of a seismo-acoustic array with 2.5 km aperture, designed and installed in 2009 in the epicentral Vrancea seismogenic area, at the Carpathian Arc bend in Romania. The array belongs to the National Institute for Earth Physics and includes four infrasound stations and seven seismic stations. The purpose of this study is to analyze the ability of Ploştina infrasound array to detect and discriminate accidental chemical explosions located at regional distances. Two recent chemical explosions produced in Cyprus (2011) and in South-eastern Bulgaria (2012) are investigated. The multi-channel correlation algorithm is applied for the identification and characterization of the infrasound signals generated by the two explosive events, as concerns back azimuth, propagation velocity and frequency content. By applying this approach, we prove the efficiency of Ploştina array in identifying and characterizing infrasound signals caused by accidental chemical explosions.

Authors:
Tătaru D., Năstase E., Toma-Dănilă D.

Abstract:

Authors:
Tătaru D., Poiată N., Grecu B., Radulian M., Popa M.

Abstract:
Analysis and characterization of seismicity and its changes is a powerful way to detect, monitor and discriminate between the different types of seismic energy radiations. Modern seismic networks can be today seen as arrays, or antennas, of increasing density and spatial coverage, recording continuous high-quality signals, and making it possible to explore time and frequency scales at which seismic processes were essentially unknown. Seismic activity in Romania covers a wide range of tectonic environments from intermediate depth seismicity in the Vrancea area to the shallow crustal sources, such as those of Dobrogea and Banat. Moreover, Romania is a site of various mining and oil exploitation campaigns. A significant part of seismicity is associated to such industrial contexts as: quarries (Dobrogea, Campulung, Rosia Poieni), dams (Bicaz, Vidraru), mining (Petrosani), or oil exploitations. These kinds of seismic activity have an increasing impact on society. The aim of this study is to present developments towards an integrated framework for detection, location and characterization of seismic sources associated to natural (tectonic) and anthropogenic environments in Romania. We discuss a detection and location methodology based upon most novel developments in the field of seismic source observation that can be applied to a large range of observations, from regular tectonic earthquakes to the micro-seismicity and seismic swarm observations. The performance of the method is tested on a pilot case of the 2013 seismic crises near the city of Galati and the potential fmiher developments and applications are discussed in the light of a more general context.

Authors:
Tătaru D., Toma-Dănilă D., Năstase E.

Abstract:
In order to remain essential cultural and educational institutions, exhibitions and museums need to adapt to the times we live in and to the pace of technology and human interests. Through this paper, we present our own experience and research in developing a state-of-the art earthquake-related exhibition that meets the demands of our times and efficiently addresses a large and diverse target audience. The MOBEE (MOBile Earthquake Exhibition) Project tackles a very problematic topic in regard to the present and future of Romania: the key role of education, in the perspective of a future major earthquake. The project is the only initiative of this kind in Romania, a country where the lessons of previous destructive earthquakes (of 1940 and 1977) seem to be neglected. One of the main goals of the exhibition is to provide a reliable, attractive and- up-to-date source of information regarding earthquakes, leading to mitigation by education. The initiative translates modern approaches into science, arts and computer science into end-products with a direct impact in forming (awakening) and developing the interest for earth science. We provide an insight on how and why new technologies and concepts like large-scale 3D printed maps and models, digital animations and app development, hands-on experiments, or flexible content were put to use. We hope that by sharing our experience we can help and stimulate other similar initiatives and propagate the mobile exhibition concept, as a form of reaching the nowadays audiences (besides the online environment, which we also cover).

Authors:
Tătaru D., Toma-Dănilă D., Năstase E., Zaharia B., Grecu B.

Abstract:
Seismology is a multidisciplinary research domain known as a blend of theoretical and applied research in Earth science and physics, dealing mainly with the fundamental study of earthquakes, seismic waves but also prospecting and recovery of natural resources. Seismology also made possible to look into the deep inaccessible interior of the Earth at depths of up to thousands of kilometers and to extract information about the earthquake parameters and wave propagation and use it to evaluate seismic hazard and risk to buildings, power plants and other infrastructure. And not known by many, seismology was and is used to monitor clandestine nuclear explosions and thus brings a contribution to maintain peace on earth. All the mentions above make seismology a perfect topic to communicate the very essence of science, raise the enthusiasm and excitement of students for scientific discoveries and show the importance of understanding the complexity of our planet - all this knowledge contributing to the building of a more resilient society. Even if, at a first glance, all behind seismology seems to be a quite complicated research, in fact, many fundamental theories and facts can be comprehended from the very first educational grades. That is why, looking backwards, seismology also provides opportunities to teach many science, math and technology concepts and skills to learners of all ages. Unfortunately, as studies have shown, geoscience topics get less and less within the science curriculum, only briefly into geography courses. A change can come from seismology projects that aim to influence the future development of the science curriculum by proving the use of earthquakes and seismology in learning school physics, math and geography. Such a pilot project - entitled Romanian Educational Seismic Network (ROEDUSEIS) has been under implementation for 5 years in more than ten Romanian high schools. Beyond the common objectives and advantages that such a project brought to participating schools (seismometer in the classroom, real time seismic data viewing and processing), we succeeded to propose an interdisciplinary school choice discipline (related to physics, geography & ICT), that is taught in five 11th grade classes, having seismology as a centralizing theme. It comprises lessons on force, friction, wave propagation, and engineering design as well as plate tectonics and driving forces. The role of technology in accessing, processing and using information is underlined through the use of dedicated educational software for detecting, locating and analyzing explosions and earthquakes. For all the other schools we embedded the lessons in existing schools topics rather than creating a new module. In fact, seismology offers unique opportunities to enrich science and physics curriculum and finding creative teachers that are able to deliver innovative lessons, thus improving the chances that students become more interested in science even as a future career path. And thus is a natural transition to another clearly state objective of a seismology education project: to improve the quality of science, technology, engineering and mathematics (STEM) career guidance for students, to help them make informed post16 subject choices.

Authors:
Tătaru D., Zaharia B., Grecu B., Țibu S., Brișan N., Georgescu E.S.

Abstract:
The Romanian Educational Seismic Network project is an educational initiative which launches a challenge for the Romanian educational system: how to use seismology in classrooms for raising awareness on earthquake risk as well as a tool for influencing the development of science curriculum. The project is piloted in nine schools. Educational materials were developed comprising theoretical aspects, activities and experiments related to earthquakes and their effects. First Romanian educational seismic network was built and workshops for teachers were organized with the purpose of showing how Earth Science topics can be taught in classrooms based on the concept “learning by doing”.

Authors:
Tătaru D., Bican-Brisan N., Zaharia B., Grecu B., Toma-Dănilă D., Țibu S.

Abstract:

Authors:
Toma-Dănilă D., Tătaru D.

Abstract:

Authors:
Bălan F.S., Apostol B.F.

Abstract:

Authors:
Bostan D.C., Manea E.F., Ștefan S.

Abstract:
Within this paper the cloudiness spatial and seasonal distribution is analyzed for the eastern part of Romania (Moldavia Region) for a five years period (2006 2010). Hourly data (total and partial cloudiness) from 14 surface observation stations have been used to build a small data base. In order to increase the cloudiness accuracy, an algorithm to derive the partial cloudiness has been applied. This data base allowed us to generate an improved climatology of total and partial cloudiness for Moldavia Region. As an application, the built data base has been used to validate the cloudiness simulated by the mesoscale numerical weather prediction model ALARO. The model results were compared to observation for one year. The obtained statistics have been used to tune the free parameter of the model cloudiness parameterization scheme.

Authors:
Bălă A., Grecu B., Arion C., Popescu E., Toma-Dănilă D.

Abstract:
Different studies focused on the Vrancea subcrustal source of earthquakes pointed out the strong lateral inhomogeneous distribution of the seismic radiation. This implies characteristic macroseismic distributions, extremely elongated along NE-SW direction, and sharply restraint toward NW and SE. Many authors ascribed this particular radiation pattern to the predominant focal mechanism noticed for the major Vrancea shocks [1]. However, a few papers showed that the lateral variation in the subcrustal region seems to be more important (e.g., [2];[3]). We plan in this paper to asses the importance of the source and path of the Vrancea earthquakes on the ground motion parameters in the area of Bucharest. The fault plane solutions of most Vrancea earthquakes indicate a nearly pure thrust mechanism with the B-axis striking NE, which is typical for the strongest events. However there are some earthquakes that do not follow this pattern. We analyze the influence of focal mechanism radiation and source frequency content on the ground motion parameters in Bucharest area. The role of the focal mechanism of the earthquakes and of the depth at which the earthquakes occur determine the path on which seismic waves are propagating to the surface. A significant role is played by the variation of the lithosphere structure between the depth of earthquakes (60-160 km) and the surface, for the seismic motion recorded in the Bucharest area. The analysis of a recent set of intermediate depth earthquakes with Mw > 4.5, for which the focal mechanism have been computed, show the significant role played by the variation of these parameters in respect to the seismic motion recorded in the Bucharest area. These parameters might be in some cases as important as the site effects in establishing the local seismic hazard for the Bucharest City.

Authors:
Ștefan S., Roman I.

Abstract:
The aim of this paper is to analyze the temporal variability of Particulate Matter mass concentrations in connection with air circulation, for eight rural sites situated in the Central and Eastern parts of Europe. The stations from Poland, Hungary and Romania are rural stations without sources of pollutants. The analysis covers four winters, between December 2004 and February 2008. The pollution episodes were selected to explain air circulation influence. The results show that the causes of pollution were local, due to high mean sea level pressure and the blocking, as air circulation on large scale, was dominant in the cases of enhanced pollution in the selected area.

Authors:
Ioane D., Șerban A., Diaconescu M., Chițea F., Caragea I.

Abstract:
A sudden seismological unrest started on mid-September 2013 in the Izvoarele village area, earthquakes and subterranean noises occurring almost continuously for a month. The seismological monitoring provided more than 370 seismic events, with magnitude ranging between 0.3 and 4.0 and depth ranging from 0.3 km to more than 30 km. Considering the historical seismicity, studied during the end of the XIXth century and the first half of the XXth century by means of seismic intensity, the Izvoarele-Galati area represents the southern end of a N-S high seismicity sector developed between Barlad and Galati. Based on these observations regarding epicentral areas and destructive effects, several NW-SE to N-S trending lines of "seismic sensitivity" were interpreted at that time. The study of the 2013 seismic sequence showed that most earthquakes provided magnitudes between 0.3 and 1.5, ca 10% having higher magnitudes (16 more than 2.5, 11 more than 3.0 and 8 more than 3.5). The relationship between Magnitude and Depth for the recorded seismic events displays a scattered distribution of the 2013 seismic events with low magnitude values (0.3 to 2.0), most of them included in the 0.1-10.0 km depth interval. Higher magnitude earthquakes (2.0 to 4.0) were generated in a smaller range of depth values (3.0 to 7.0). The relationship between Magnitude and Time illustrates three main stages of high seismicity for the studied 2013 seismological event: September 25-27, September 30 to October 7 and October 12-15, with exceptionally dense seismic activity during October 2-5. Considering the spatial development of the active seismic zone, two parallel lines trending NE-SW in the area were observed when plotting the earthquakes epicentres with magnitude higher than 3.0. Active segments of a regional NE-SW trending fault system were interpreted this way. The seismic events that occurred at depths higher than 10 km illustrated several distinct episodes during the intense seismological activity: September 23 and 28-29; October 4-5, 15 and 20-21. A quite close spatial association was found between the 2013 high seismicity area and an oil exploitation facility, the extracting works dating here from the second half of the XXth century. The oil reservoirs are shallow, located between 0.5 and 0.7 km depth, the sandy deposits being sealed by faults or compact crystalline rocks. Induced seismicity might be expected as brine is being injected during time to replace the extracted oil. A characteristic of this geological structure, that might be important in understanding the unusual seismicity and subterranean noises, is represented by the thin marl beds separating the sandy beds, which collapse in case of a sudden pressure decrease and determine the flooding of the oil reservoir.

Authors:
Mărmureanu A., Craiu G., Craiu A., Rădulescu S, Neagoe C., Ionescu C.

Abstract:
Providing warning notification several seconds before dangerous earthquake waves arrive at a target site reduces the property damages and human casualties. Most earthquake early warning systems (EEWS) developed are either regional (“network based”) or on-site (“stand alone”) systems. The recent upgrade of the seismic network in Romania with high dynamic range accelerometers allows recording of moderate to large magnitude earthquakes at very close epicentral distances (less than 10–20 km). This allows an increase of the warning lead-time (the time difference between the alert notification time and the arrival time of potentially destructive waves at a given target). The seismicity of Romania is significantly affected by earthquakes produced by the Vrancea seismic source with intermediate depth events (three shocks/century with magnitude Mw greater than 7.0). In this paper we present the performance of the seismic network in rapidly locate events occurring in the Vrancea area. Since rapid location of earthquakes is the first step in issuing early warning notifications, by reducing the time of the first valid location will lead to an increase the lead-time interval. Also rapid location of events will allow a future upgrade of EEWS to cover the entire Romanian territory.

Authors:
Pavel F., Văcăreanu R., Radulian M., Cioflan C.O.

Abstract:
This paper evaluates possible directional effects from strong ground motions recorded during the last four significant subcrustal earthquakes produced in the Vrancea seismic zone (Romania) in August 1986 (M (W) = 7.1), May 1990 (M (W) = 6.9 and 6.4) and October 2004 (M (W) = 6.0). Several measures of the horizontal component of the ground motion given in the literature (Boore et al., 2006; Boore, 2010) are computed and are related to the geometric mean of the as-recorded horizontal components. ANOVA method is applied in order to quantify the influence of the earthquake magnitude and of the soil class on some strong ground motion parameters (e.g. Arias intensity, PGV/PGA, or mean period T (M)). The study of the directional effects is performed using the distribution of I (JMA) and of the rotation angle corresponding to a measure of the horizontal component of the ground motion (RotD100) and the results reveal a visible directional pattern for I (JMA), while in the case of RotD100 the directional patterns are less visible.

Authors:
Văcăreanu R., Radulian M., Iancovici M., Pavel F., Neagu C.

Abstract:
A next generation ground motion model for the prediction of spectral accelerations both in the fore-arc and back-arc regions of the Carpathians Mountains is developed in this research for the Vrancea intermediate depth seismic source in Romania. This ground motion prediction equation (GMPE) is an updated version of the model given in Vacareanu et al. [2014] and is applicable in both the fore-arc and the back-arc regions. The strong ground motion database from which the prediction model is derived consists of over 700 triaxial accelerograms from Vrancea subcrustal seismic events, as well as from other intermediate-depth earthquakes produced in other seismically active regions in the world. The applicability of this ground motion prediction model in both the fore-arc and the back-arc region is tested using the analysis of residuals. Moreover, the appropriateness of this GMPE for soil classes B and C defined in EN 1998-1, as well as for average soil conditions is investigated. All results suggest that this model is an improvement of the previous versions of ground motion prediction equations for Vrancea intermediate-depth seismic source and its use in both the fore-arc and the back-arc regions make it a reliable candidate for more accurate seismic hazard studies of Romania.

Authors:
Maggipinto T., Biagi P.F., Colella R., Schiavulli L., Ligonzo T., Ermini A., Martinelli G., Moldovan I.A., Silva H., Contadakis M., Skeberis C., Zaharis Z., Scordilis E., Katzis K., Buyuksarac A. and D’Amico S.

Abstract:
On October 12, 2013, an earthquake with Mw = 6.5 occurred in the southern Hellenic Arc, approximately 20 km off the west coast of Crete. The main shock, the focal depth of which is on the order of 40 km, was followed by aftershocks felt in the nearby cities and villages, although the aftershock sequence was poor. The epicentre was located at approximately 60 km from a radio receiver in Crete (CRE), which belongs to the European VLF/LF Radio Network. Several days before the earthquake, a clear disturbance occurred in one of the ten radio signals that the CRE receiver sampled. The disturbance, which can be considered an anomaly, appeared in the 216 kHz radio signal radiated by the Radio Monte Carlo (MCO) transmitter. The radio path MCO-CRE crossed directly over the epicentre area of the aforementioned earthquake. In this work, we present a detailed analysis of the MCO signal anomaly using spectral tools. We also investigate the behaviour of other radio signals sampled by the CRE receiver and consider other possible causes of disturbances on the MCO radio signal. We conclude that the disturbance in the MCO radio signal is a convincingly possible precursor of the earthquake in Crete. Emission of electromagnetic waves with a frequency band that includes 216 kHz from the focal zone of the earthquake can provide a satisfactory explanation of the radio anomaly.

Authors:
Dolea P., Cristea O., Dascal P.V., Moldovan I.A., Biagi P.F.

Abstract:
In the last decades, one of the main research directions in identifying seismic precursors involved monitoring VLF (Very Low Frequency) and LF (Low Frequency) radio waves and analysing their propagation characteristics. Essentially this method consists of monitoring different available VLF and LF transmitters from long distance reception points. The received signal has two major components: the ground wave and the sky wave, where the sky wave propagates by reflection on the lower layers of the ionosphere. It is assumed that before and during major earthquakes, unusual changes may occur in the lower layers of the ionosphere, such as the modification of the charged particles number density and the altitude of the reflection zone. Therefore, these unusual changes in the ionosphere may generate unusual variations in the received signal level...

Authors:
Pavel F., Văcăreanu R., Douglas J., Radulian M., Cioflan C.O., Barbat A.

Abstract:
The probabilistic seismic hazard analysis for Romania is revisited within the framework of the BIGSEES national research project (http://infp.infp.ro/bigsees/default.htm) financed by the Romanian Ministry of Education and Scientific Research in the period 2012–2016. The scope of this project is to provide a refined description of the seismic action for Romanian sites according to the requirements of Eurocode 8. To this aim, the seismicity of all the sources influencing the Romanian territory is updated based on new data acquired in recent years. The ground-motion models used in the analysis, as well as their corresponding weights, are selected based on the results from several recent papers also published within the framework of the BIGSEES project. The seismic hazard analysis for Romania performed in this study are based on the traditional Cornell-McGuire approach. Finally, the results are discussed and compared with the values obtained in the recently completed SHARE research project. The BIGSEES and SHARE results are not directly comparable since the considered soil conditions are different—actual soil classes for BIGSEES and rock for SHARE. Nevertheless, the analyses of the seismic hazard results for 200 sites in Romania reveal considerable differences between the seismic hazard levels obtained in the present study and the SHARE results and point out the need for further analyses and thorough discussions related to the two seismic hazard models, especially in the light of a possible future harmonized hazard map for Europe.

Authors:
Toma-Dănilă D., Zulfikar C., Manea E.F., Cioflan C.O.

Abstract:
Bucharest, capital of Romania, is one of the most exposed big cities in Europe to seismic damage, due to the intermediate-depth earthquakes in the Vrancea region, to the vulnerable building stock and local soil conditions. This paper tries to answer very important questions related to the seismic risk at city scale that were not yet adequately answered. First, we analyze and highlight the bottlenecks of previous risk-related studies. Based on new researches in the hazard of Bucharest (recent microzonation map and groundmotion prediction equations, reprocessed real recorded data) and in vulnerability assessment (analytical methods, earthquake loss estimation software like SELENA and ELER, the recently implemented Near Real-Time System for Estimating the Seismic Damage in Romania) we provide an improved estimation of the number of buildings and population that could be affected, for different earthquake scenarios. A new method for enhancing the spatial resolution of the building stock data is used successfully. (C) 2015 Elsevier Ltd. All rights reserved.

Authors:
Moldovan I.A., Constantin A.P., Biagi P.F., Toma-Dănilă D., Moldovan A.S., Dolea P., Toader V.E., Maggipinto T.

Abstract:
The Romanian VLF / LF monitoring system consists in a radio receiver and the infrastructure that is necessary to record and transmit the collected data, and is part of the international initiative INFREP and was put into operation in December 2009 on the Black-Sea shore (Dobruja Seismologic Observatory - Dob-RO). Since then the system was developed by replacing the vertical antenna with a magnetic loop-type one, by installing a vertical electric field monitor and a weather station, and by designing special software for the transfer, storage and initial processing of data using the LabView software platform.

Authors:
Bălă A., Grecu B., Arion C., Popescu E., Toma-Dănilă D.

Abstract:
Providing warning notification several seconds before dangerous earthquake waves arrive at a target site reduces the property damages and human casualties. Most earthquake early warning systems (EEWS) developed are either regional ("network based") or on-site ("stand alone") systems. The recent upgrade of the seismic network in Romania with high dynamic range accelerometers allows recording of moderate to large magnitude earthquakes at very close epicentral distances (less than 10-20 km). This allows an increase of the warning lead-time (the time difference between the alert notification time and the arrival time of potentially destructive waves at a given target). The seismicity of Romania is significantly affected by earthquakes produced by the Vrancea seismic source with intermediate depth events (three shocks/century with magnitude Mw greater than 7.0). In this paper we present the performance of the seismic network in rapidly locate events occurring in the Vrancea area. Since rapid location of earthquakes is the first step in issuing early warning notifications, by reducing the time of the first valid location will lead to an increase the lead-time interval. Also rapid location of events will allow a future upgrade of EEWS to cover the entire Romanian territory.

Authors:
Bălă A., Răileanu V., C. Dinu, M. Diaconescu

Abstract:
The most significant seismicity in Romania is located in a relatively small area-the Vrancea seismogenic zone, where 2-3 intermediate depth strong earthquakes (Mw>7.0) occur in a century. Although the crustal seismicity is dispersed in several zones of country, only in a few areas the observed magnitudes exceeded Mw=6.0. Nevertheless some crustal earthquakes that occurred in the past have resulted in damages and even casualties. These facts imposed the taking into account of crustal seismicity in the seismic hazard mapping. Crustal seismicity in Romania is distributed within some belts located along of Carpathians and the Pannonian depression having a more significant concentration in the Vrancea crustal area and in the front of Eastern Carpathians bend, in the Fagaras Mountain area, in the Danubian area, Banat, Crisana, Maramures and North Dobrogea regions. A summary of the crustal seismic activity beneath the western part of Romanian is presented pointing out the most significant events known from both historical and instrumental records. The observed crustal seismicity did not exceed Mw= 5.6 excepting the Fagaras area where the strongest events reached up to Mw=6.5. For each crustal seismogenic zone the main fault systems which can account for the local seismicity are presented. This study presents a correlation of seismicity data with the local tectonics. Special attention is focused on the Transylvanian Basin and on the Pannonian sector where a correlation of seismicity with deep structure is better documented.

Authors:
Craiu A., Mărmureanu A., Diaconescu M., Craiu M.G., Ionescu C.

Abstract:
In this paper we present the results obtained during the study of swarm of earthquake close to the Galati city. In the last period the National Seismic Network was continuously upgraded, which allows presently to easily detect earthquakes with very low magnitudes in every seismic region of Romania. The seismogenic region of the swarm is situated between two main crustal faults, oriented SE-NW: Sf. Gheorghe fault (located in North Dobrogea, in the Scythian Platform) to the North, and Peceneaga Camena fault (which separates North Dobrogea block from the Moesian Platform) to the South. The epicentral zone belongs to a complex tectonic area, in which a secondary fault system – lying NE-SW, perpendicular to the dominant system – is present too. The seismic swarm started on September 23, 2013, close to Galati city, in Izvoarele region (Romania), and lasted until November 12, 2013. 406 earthquakes were recorded during several phases of seismic activity. The strongest events – a magnitude 3.9 earthquake, occurred on September 29, and two ML 3.8 shocks, which occurred on October 3 and October 4, respectively, were accompanied by specific seismicity bursts. The spatial distribution of the epicenters, which are aligned in NE-SW direction, indicates that the seismic swarm was generated by the second fault system. The focal mechanisms show normal slip, with one of the nodal planes oriented roughly in NE-SW direction. The results are discussed and interpreted in relation with the regional seismotectonics, our study aiming to emphasize new elements and implications for seismic hazard evaluation in the Galati area. Key word: seismic swarm, focal mechanism

Authors:
Craiu A., Craiu M.G., Diaconescu M., Mărmureanu A.

Abstract:
The systematic studies of the focal mechanism solutions furnish fundamental data about some of the main factors that control the seismic phenomenon, e.g. stress field peculiarities and the types of faulting, the geometry of the faults and provide critical information for global, regional and local tectonic studies, as well as for many types of seismological investigations. In the last few years were recorded some significant earthquakes in the Vrancea subcrustal domain and in other seismic regions at crustal depths. The National Seismic Network was continuously updated in the last years and now the recordings of these events contribute to a complete database and are very important to seismology and seismic hazard assessment studies. The substantial increase in the seismic recordings and the azimuthal gap leads to a more precise knowledge of focal mechanism, structure and source parameters. The seismicity of Romania is distributed in several epicentral zones: Vrancea, Fagaras-Campulung, Banat, Crisana, Maramures, and Dobrogea. The main goal of this paper is to study seismicity evolution and the focal mechanism analysis of recent earthquakes occurred in Romania (in last five years) and their correlation with the average stress field. We have determined fault plane solutions and analyzed the seismic activity recorded on the Romania territory in connection with seismogenic zones. At the same time, our results are integrated and interpreted in connection with the stress field characteristics, deduced from the available fault plane solutions on different depth intervals.

Authors:
Craiu M.G., Mărmureanu A., Craiu A., Ionescu C.

Abstract:

Authors:
Diaconescu M., Craiu A., Toma-Dănilă D.

Abstract:
Earthquakes from the Fagaras seismic zone originate in the Southern Carpathians area and they have foci located East and West of the OLT Valley. In this area the largest earthquake occurred after the Vrancea area on 26.01.1916, with an intensity estimated to have exceeded level 7 in the epicenter (Mw= 6.4), which was followed by numerous aftershocks extended about 6 months. On the same day as the main earthquake of 6.4 (Mw) also produced other three quakes one of 5.2 (Mw), one of 5 (Mw), and one of 4.4 (M-W). The series of earthquakes in 1916 appears to be due not to an outbreak not only, but tectonic movements along a line on the alignment Băbuieşti-Confluence-Piscu Negru. Other seismic lines are: Călimăneşti- Coteşti-Horezu and Arefu-Ismailia-Govora where I <5 degrees.The earthquakes from the 1916 seismic sequence have shifted from North-West to South-East. Earthquakes have occurred in the south have North West direction on deep fractures following hercinic ages, and the Northeast directions of the Alpine age. The fault plane solutions of some more recent earthquakes showed a shear mechanism through compression and are associated with the deep faults oriented W-E or N-S, faults associated with the thrust of the Supragetic domain over the Getic domain. Note that the total of 474 events recorded between 1550 and 2014, 13 earthquakes were generated before 1900 and have the largest magnitudes (5 of them have the magnitude 6.2

Authors:
Ioane D., Șerban A., Diaconescu M., Chițea F., Caragea I.

Abstract:
A sudden seismological unrest started on mid-September 2013 in the Izvoarele village area, earthquakes and subterranean noises occurring almost continuously for a month. The seismological monitoring provided more than 370 seismic events, with magnitude ranging between 0.3 and 4.0 and depth ranging from 0.3 km to more than 30 km. Considering the historical seismicity, studied during the end of the XIX th century and the first half of the XX th century by means of seismic intensity, the Izvoarele–Galati area represents the southern end of a N-S high seismicity sector developed between Barlad and Galati. Based on these observations regarding epicentral areas and destructive effects, several NW-SE to N-S trending lines of " seismic sensitivity " were interpreted at that time. The study of the 2013 seismic sequence showed that most earthquakes provided magnitudes between 0.3 and 1.5, ca 10% having higher magnitudes (16 more than 2.5, 11 more than 3.0 and 8 more than 3.5). The relationship between Magnitude and Depth for the recorded seismic events displays a scattered distribution of the 2013 seismic events with low magnitude values (0.3 to 2.0), most of them included in the 0.1–10.0 km depth interval. Higher magnitude earthquakes (2.0 to 4.0) were generated in a smaller range of depth values (3.0 to 7.0). The relationship between Magnitude and Time illustrates three main stages of high seismicity for the studied 2013 seismological event: September 25-27, September 30 to October 7 and October 12-15, with exceptionally dense seismic activity during October 2-5. Considering the spatial development of the active seismic zone, two parallel lines trending NE-SW in the area were observed when plotting the earthquakes epicentres

Authors:
Mărmureanu A., Ionescu C., Craiu M.G., Craiu A., Tolea A.

Abstract:

Authors:
Tătaru D., Grecu B., Zaharia B., Toma-Dănilă D., Năstase

Abstract:
The Carpathian seismic belt (Vrancea Area), located in Romania, is one of the most active tectonic regions in Europe. In the last few decades, the country has experienced several major earthquakes which have claimed thousands of lives and caused significant economical damage (Vrancea, 1940; 1977; 1986). Even so, little is currently done for the general public in order to mitigate the possible effects of a future major earthquake. As intermediate depth earthquakes affect a vast area (up to 400 km from the epicenter), there is a continuous need in raising awareness by sharing information and knowledge in a broader area and to a larger audience. To have a proper framework for engaging new communities and build partnerships, with benefit for all parties involved, a series of pilot projects have been initiated by National Institute for Earth Physics (NIEP) researchers. Here we will focus on just two of them, named by their acronym: ROEDUSEIS and MOBEE. Improving public awareness and education of population is an essential part of mitigating the natural risks. Starting this effort at the level of schools and opening the doors for the wide public to take part, will certainly be a way to increase the chances of success. Our view is that the research institutes should have a leading role in providing useful data regarding the earthquakes, thus helping the better understanding of this natural phenomenon, and thus bringing its contribution to build a more resilient society.

Authors:
Tătaru D., Grecu B., Zaharia B., Oros E., Bălă A.

Abstract:
As a result of the deployment of the permanent Romanian broadband stations in the last 10 years, valuable data for seismicity and crustal structure studies in Romania has become available. Complementary to this dataset, during a joint project between University of Leeds, UK and National Institute for Earth Physics, Romania (South Carpathian Project – SCP), 33 broadband seismic stations autonomously operated in the western part of the country and continuously provided data for two years (2009-2011). This project offered a good opportunity to study the seismicity and structure of western Romania. First, we study the spatial distribution of epicenters and temporal distribution of origin times of the events occurred between July 2009 and June 2011 and we show that many of the seismic events grouped into clusters are of artificial origin. We also investigate the background seismic noise at stations deployed during SCP experiment and notable diurnal and seasonal variations have been observed at most of the stations. Finally, we used the receiver function technique and a joint inversion technique of receiver function and Rayleigh wave dispersion to derive velocity models for each seismic station location. The results show a thin crust for stations located inside the Pannonian basin (28-30 km). The stations within the Southern and Central Carpathian Orogen are characterized by crustal depths of ~35 km. For two station located in the Apuseni Mountains the Moho discontinuity is replace by a transition zone extended between 36 to 40 km depth.

Authors:
Ivan M., Ghica D.V., Gosar A., Hatzidimitriou P., Hofstetter R., Polat G., Wang R.J.

Abstract:
Lowermost mantle velocity in the area 15A degrees S-70A degrees N latitude/60A degrees W-5A degrees W longitude is estimated using two groups of observations, complementary to each other. There are 894 Pdif observations at stations in the Balkan and Eastern Mediterranean areas from 15 major earthquakes in Central and South America. Another 218 Pdif observations are associated with four earthquakes in Greece/Turkey and one event in Africa, recorded by American stations. A Pdif slowness tomographic approach of the structures immediately above the core-to-mantle boundary (CMB) is used, incorporating corrections for ellipticity, station elevation and velocity perturbations along the ray path. A low-velocity zone above CMB with a large geographical extent, approximately in the area (35-65A degrees N) x (40-20A degrees W), appears to have the velocity perturbations exceeding the value actually assumed by some global models. Most likely, it is extended beneath western Africa. A high-velocity area is observed west of the low-velocity zone. The results suggest that both Cape Verde and Azorean islands are located near transition areas from low-to-high velocity values in the lowermost mantle.

Authors:
Mărmureanu G., Mărmureanu A., Cioflan C.O.

Abstract:
The nonlinear seismology is the rule, The linear seismology is the exception. Paraphrasing Tullio Levi-Civita The leading question is: how many cities, villages, metropolitan areas etc. in seismic regions are constructed on rock sites? Most of them are located on alluvial deposits/ sediments, on Quaternary layers or in river valleys. In last book written by Peter M. Shearer, Professor of Geophysics at University of California, we can find, in total, only 12 rows about non-linear seismology(page 176).Among others are the following conclusions:(i)-Strong ground accelerations from large earthquakes can produce a non-linear response in shallow soils; (ii)-When a non-linear site response is present, then the shaking from large earthquakes cannot be predicted by simple scaling of records from small earthquakes; (iii)-This is an active area of research in strong motion and engineering seismology. On the other hand, Aki wrote: Nonlinear amplification at sediments sites appears to be more pervasive than seismologists used to think…Any attempt at seismic zonation must take into account the local site condition and this nonlinear amplification(Aki, A., Local Site Effects on Weak and Strong Ground Motion, Tectonophysics,218,93-111,1993). The difficulty to seismologists in demonstrating the nonlinear site effects has been due to the effect being overshadowed by the overall patterns of shock generation and propagation. In other words, the seismological detection of the nonlinear site effects requires a simultaneous understanding and separating of the effects of earthquake source, propagation path and local geological site conditions. To see the actual influence of nonlinearity of the whole system (seismic source-path propagation-local geological structure) the authors used to study the response spectra because they are the last in this chain and, of course, that they are the ones who are taken into account in seismic design of all structures Stress-strain relationships for soils are usually nonlinear, soil stiffness decreases and internal damping increases with increasing shear strain during of strong earthquakes. There is a strong nonlinear dependence of the spectral amplification factors(SAF) on earthquake magnitude for all seismic stations on Romanian territory on extra-Carpathian area (Iasi, Bacau, Focsani, Bucharest etc.). Median values of SAF for last strong Vrancea earthquakes are decreasing from 4.16(May 31,1990;Mw=6.4),to 3.63 (May 30,1990;Mw=6.9) and to 3.26 (August 30, 1986; Mw=7.1) .The novelty and the complexity degree comes from the fact that for first time, the final decision for NPP Cernavoda site was also based on local strong nonlinear spectral amplifications for strong earthquakes and used in last "STRESS TEST" asked by IAEA Vienna in 2011. The present analysis indicates that the effect of nonlinearity could be very important and if the analysis is made for peak accelerations, it is 48.87% and for stronger earthquakes it will be bigger. The authors are coming with new recorded data which will open up a new challenge for seismologists studying nonlinear site effects in 2-D and 3-D irregular geological structures, leading them to a fascinating research subject in earth physics(Aki,1993, p.108,idem),in nonlinear seismology and,finally, in a real evaluation of earthquake risk and loss estimates.

Authors:
Moldovan I.A., Constantin A.P., Biagi P.F., Toma-Dănilă D., Moldovan A.S., Dolea P., Toader V.E., Maggipinto T.

Abstract:
The Romanian VLF / LF monitoring system consists of a radio receiver and the infrastructure that is necessary to record and transmit the collected data, and is part of the international initiative INFREP and was put into operation in December 2009 on the Black-Sea shore (Dobruja Seismologic Observatory – Dob-RO). Since then the system was developed by replacing the vertical antenna with a magnetic loop-type one, by installing a vertical electric field monitor and a weather station, and by designing special software for the transfer, storage, and initial processing of data using the LabView software platform.

Authors:
Oikonomou C., Toma-Dănilă D., Haralambous H., Muntean A., Moldovan I.A.

Abstract:
We examine the lithosphere-atmosphere-ionosphere interaction with respect to earthquake events using Total Electron Content (TEC) data deriving from the Romanian permanent GPS network by applying three different techniques: a) estimation of TEC deviations from the mean state, b) Cross-Correlation Analysis and c) Spectral Analysis. The analysis concerns four seismic events that took place in Romania with magnitude ranging from 5.2 to 6.0. The aim is to identify and study possible ionospheric precursory phenomena linked to these seismic events.

Authors:
Toader, V.E., Moldovan I.A., Ionescu C.

Abstract:
The paper describes a complex multidisciplinary monitoring system designed for Vrancea seismic area (bending area of Carpathians Mountains). This includes hardware (stations with sensors, acquisition and communication equipment) and software for data processing in real time. The result of this work is the growth of an alert service through: perfecting risk evaluation, seismic and climate forecast, informing the decision factors regarding the impact minimization of natural disasters and the education of the population. The information from database will help the scientists to develop the system and to improve their knowledge for other applications. A monitoring network involves a multidisciplinary activity that highlights the interdependence of environmental factors (air, earth) and their balance under normal conditions. Weather or seismic events represent the point of maximum imbalance. Electromagnetic, infrasound, seismoacoustic at high frequencies, air ionization and solar radiation monitoring, in correlation with global and local environmental factors (including seismic zones), is a new approach for atmospheric study in our area. Figure 1 describes a global structure of system. Data are acquired from ground (National Institute for Earth Physics - NIEP seismic stations) and satellites.

Authors:
Bălă A., Răileanu V., Dinu C., Diaconescu M.

Abstract:
The most significant seismicity in Romania is located in a relatively small area - the Vrancea seismogenic zone, where 2-3 intermediate depth strong earthquakes (Mw > 7.0) occur in a century. Although the crustal seismicity is dispersed in several zones of country, only in a few areas the observed magnitudes exceeded Mw = 6.0. Nevertheless some crustal earthquakes that occurred in the past have resulted in damages and even casualties. These facts imposed the taking into account of crustal seismicity in the seismic hazard mapping. Crustal seismicity in Romania is distributed within some belts located along of Carpathians and the Pannonian depression having a more significant concentration in the Vrancea crustal area and in the front of Eastern Carpathians bend, in the Fagaras Mountain area, in the Danubian area, Banat, Crisana, Maramures and North Dobrogea regions. A summary on the crustal seismic activity beneath the Romanian is presented pointing out the most significant events known from both historical and instrumental records. The observed crustal seismicity did not exceed M-w = 5.6 excepting the Fagaras area where the strongest events reached up to M-w = 6.5. For each crustal seismogenic zone the main fault systems which can account for the local seismicity are presented. This study presents a correlation of seismicity data with the local tectonics. A special attention is focused on foreland of the Carpathian orogen and on the Pannonian sector where a correlation of seismicity with deep structure is better documented.

Authors:
Stancu I., Ghica D., Radulian M., Ionescu C.

Abstract:
The Infrasound Plostina Array (IPLOR) is an acoustic array of 2.5 km aperture designed and installed in 2009 in the epicentral Vrancea seismogenic area, at the Carpathian Arc bend in Romania. The Network belongs to the National Institute for Earth Physics (NIEP) and includes 4 infrasound stations and 7 seismic stations. The goal of the present study is to analyze the capacity of the infrasound array of Plostina (Romania) to detect and discriminate quarry blasts from local earthquakes. More than 50% of the shallow seismicity annually recorded in Romania is coming from industrial blasts. Plostina network description and signal processing procedures are discussed in Section 2, Data and Methods. The results of this study are presented in Section 3, and the final discussions conclusions in the end.

Authors:
Stancu I., Ghica D., Radulian M.

Abstract:
Volcanic eruptions represent excellent calibration sources for the IMS infrasound network. The location is precisely known, and the energy released during explosive eruptions may be large enough to generate infrasound waves propagated thousands of kilometers. The purpose of this study is to analyze the network capacity of infrasound from Plostina (Romania) to detect volcanic eruptions. The description of the Plostina network and signal processing procedures are discussed in Section 2, data and methods. The results and discussion of this study are presented in Section 3 and the conclusions at the end.

Authors:
Toader V. E., Popescu I., Moldovan I. A., Ionescu C.

Abstract:
Vrancea's seismicity (Curvature Carpathian mountains) recorded in 2013 an energy discontinuity preceded by the highest seismic inactivity according to the Romanian National Institute for Earth Physics. The energy is calculated based on the local magnitude (Richter), and is cumulative. Vrancea is the most important seismic region from Eastern Europe through its intermediate depth earthquakes. Energy variations can be linearly approximated due to the constant rate of earthquake occurrences. This allows to forecast the magnitude using the inverse energy-magnitude relationship. Periods longer than 5-8 days without earthquakes are followed by a more intense seismic activity. This paper analyses the evolution of seismicity in several Romanian regions that have similar energy deviations. The analysis was performed using a software tool developed by the authors of this paper. Energy discontinuity can be precursors to earthquakes greater than 7R. The analysis used information from NIEP and the European-Mediterranean Seismological Centre (EMSC) database.

Authors:
Mărmureanu G., Cioflan C.O., Mărmureanu A., Ionescu C., Manea E.F.

Abstract:
In seismic hazard evaluation and risk mitigation, there are many random and epistemic uncertainties. On the another hand, the researches in this area as part of knowledge are with rest, that is, the results are with interpretable questions with open answers. The knowledge cannot be exhausted by results. The authors developed in last time the concept of “Nonlinear Seismology – The Seismology of the XXI Century” (Marmureanu et al. Nonlinear seismology-the seismology of XXI century. In: Modern seismology perspectives, vol 105. Springer, New York, pp 49–70, 2005). The leading question is: how many cities, villages, metropolitan areas, etc., in seismic regions are constructed on rock? Most of them are located on soil deposits. A soil is of basic type sand or gravel (termed coarse soils), silt or clay (termed fine soils), etc. Strong ground accelerations from large earthquakes can produce a nonlinear response in shallow soils. This can be studied by comparing surface and borehole seismic records for earthquakes of different sizes. When a nonlinear site response is present, then the shaking from large earthquakes cannot be predicted by simple scaling of records from small earthquakes (Shearer, Introduction to seismology, 2nd edn. Cambridge University Press, Cambridge, 2009). Nonlinear amplification at sediments sites appears to be more pervasive than seismologists used to think…Any attempt at seismic zonation must take into account the local site condition and this nonlinear amplification (Aki, Tectonophysics 218:93–111, 1993). The difficulty for seismologists is to demonstrate the nonlinear site effects, these being overshadowed by the overall patterns of shock generation and propagation. In other words, the seismological detection of the nonlinear site effects requires a simultaneous understanding/knowledge of earthquake source, propagation path, and local geological site conditions. To see the actual influence of nonlinearity of the whole system (seismic source-path propagation-local geological structure), the authors used to study the free field response spectra which are the last in this chain and are taken into account in seismic design of all structures. Soils from the local geological structure at the recording site exhibit a strong nonlinear behavior under cyclic loading conditions and although they have many common mechanical properties, the use of different models to describe their seismic behavior is required. The studies made by the authors in this chapter show that using real spectral amplification factors (SAF), amplifications showing local effects, have values which differ totally from those of crustal earthquakes. The spectral amplifications highlight strong nonlinear response of soil composed of fractured limestone, limestone with clay, marl, sands, clay, etc., and these amplifications are strongly dependent of earthquake magnitude and nature of soils from site. Finally, these amplifiers are compared to those from Regulatory Guide 1.60 of the U. S. Atomic Energy Commission (Design response spectra for seismic design of nuclear power plants. Regulatory Guide 1.60. Rev. 1, Washington, D.C., 1973) which can be used only for crustal earthquakes and not for deep and strong Vrancea earthquakes from Romania. The study of the nonlinear behavior of soils during strong earthquakes may clarify uncertainties in ground motion prediction equations used by probabilistic and classical deterministic seismic hazard analysis.

Authors:
Maggipinto T., Biagi P.F., Colella R., Schiavulli L., Ligonzo T., Ermini A., Martinelli G., Moldovan I.A., Silva H., Contadakis M., Skeberis C., Zaharis Z., Scordilis E., Katzis K., Buyuksarac A., D’Amico S.

Abstract:
On October 12, 2013, an earthquake with M-w = 6.5 occurred in the southern Hellenic Arc, approximately 20 km off the west coast of Crete. The main shock, the focal depth of which is on the order of 40 km, was followed by aftershocks felt in the nearby cities and villages, although the aftershock sequence was poor. The epicentre was located at approximately 60 km from a radio receiver in Crete (CRE), which belongs to the European VLF/LF Radio Network. Several days before the earthquake, a clear disturbance occurred in one of the ten radio signals that the CRE receiver sampled. The disturbance, which can be considered an anomaly, appeared in the 216 kHz radio signal radiated by the Radio Monte Carlo (MCO) transmitter. The radio path MCO-CRE crossed directly over the epicenter area of the aforementioned earthquake. In this work, we present a detailed analysis of the MCO signal anomaly using spectral tools. We also investigate the behavior of other radio signals sampled by the CRE receiver and consider other possible causes of disturbances on the MCO radio signal. We conclude that the disturbance in the MCO radio signal is a convincingly possible precursor of the earthquake in Crete. Emission of electromagnetic waves with a frequency band that includes 216 kHz from the focal zone of the earthquake can provide a satisfactory explanation of the radio anomaly.

Authors:
Ionescu C., Marmureanu A., Marmureanu G., Solakov D., Simeonova S., Dimitrova L.

Abstract:
Providing earthquake warning notifications several seconds before dangerous earthquake waves arrive at a target site significantly reduces the property damages and the number of lives lost. Most earthquake early warning systems (EEWS) developed so far are either regional ("network-based) or "on-site" (stand-alone) systems. The recent upgrade of the seismic networks in Romania and Bulgaria with high dynamic range accelerometers allows recording of moderate-to-large magnitude earthquakes at very close epicentral distances (less than 10-20 km). This allows an increase of the early warning lead-time (the time difference between the alert notification time and the arrival time of potentially destructive waves at a given target). The Romania-Bulgaria border region is significantly affected by earthquakes occurred in both territories: on the one hand, produced by the Vrancea seismic source, with intermediate-depth events (3 shocks/century with magnitude greater than 7), and on the other hand, crustal seismicity recorded in the northern part of Bulgaria (Shabla, Dulovo, Gorna Orjahovitza). In this paper we present the rapid early warning system (REWS) for earthquakes that may affect the border areas of Romania and Bulgaria together with the software tools developed that are now used by emergency situations units in both Romania and Bulgaria.

Authors:
Apostol B.F.

Abstract:
We investigate the effect of the surface inhomogeneities (defects) on the propagation of the elastic waves in a semi-infinite isotropic solid body (half-space). A perturbation-theoretical scheme is devised for small surface defects (in comparison with the relevant elastic disturbances propagating in the body), and the elastic waves equations are solved in the first-order approximation. It is shown that surface defects generate both scattered waves localized (and propagating only) on the surface (two-dimensional waves) and scattered waves reflected back in the body. Directional effects, wave slowness and attenuation by diffusive scattering, or possible resonance effects are discussed.

Authors:
Văcăreanu R., Mărmureanu G., Pavel F., Neagu C., Cioflan C.O., Aldea A.

Abstract:
A strong-ground motion database of more than 400 records from 9 intermediate-depth earthquakes with moment magnitudes M-w >5.0 was assembled and compiled for the BIGSEES national research project. These strong ground motions are used to compute the values of the soil amplification factor which is a key parameter in the definition of the elastic response spectrum defined in Eurocode 8 (EN 1998-1). The strong ground motions are divided both in accordance with the soil category of the recording stations and with the control period To as well. The study of the acceleration response spectra as a function of magnitude, soil class and control period allows for the quantification of the amplification factors. Finally, the results obtained are compared with the design values from Eurocode 8 (EN 1998-1). This study comes at a time when Romania is harmonizing the national codes with the European design codes.

Authors:
Pavel F., Văcăreanu R., Ionescu C., Iancovici M., Sercaianu M.

Abstract:
This study focuses on the investigation of spectral characteristics of ground motions recorded from intermediate-depth Vrancea earthquakes using Newmark-Hall-type response spectrum. The database consists of more than 700 horizontal components recorded during 10 Vrancea earthquakes. In the first step of the analysis, the component-to-component variability is assessed and the corresponding influence of various parameters (earthquake magnitude, peak ground acceleration, soil class, position of the seismic station, or instrument type) is evaluated. Subsequently, the correlation between the spectral acceleration and the values of the peak ground motion parameters (acceleration, velocity, and displacement) is investigated. The analyses reveal an important influence of the magnitude and a significant influence of the soil class (in the case of large magnitude earthquakes) on the results. These findings are validated through the use of the analysis of variance (ANOVA) method. The computed response amplification factors for the Newmark-Hall type spectrum are similar with those from other studies in the literature. Finally, a check of three control periods such as T-B, T-E, and T-F of the Newmark-Hall-type spectrum yields results somewhat different from the ones given in the Romanian seismic design code P100-1 or in Eurocode 8.

Authors:
Pavel F., Văcăreanu R., Ionescu C., Iancovici M., Sercaianu M.

Abstract:
A systematic investigation of the applicability of several ground motion prediction models for Vrancea intermediate-depth seismic source is conducted in this research. Two ground motion prediction models recommended by previous evaluations (Vacareanu et al. in Bull Earthq Eng 11(6): 1867-1884, 2013a; Pavel et al. in Earthq Struct 6(1): 1-18, 2014), as well as two new state-of-the-art ground motion prediction equations (Vacareanu et al. in J Earthq Eng, 2013b; Earthq Struct 6(2): 141-161, 2014) are tested using an increased strong ground motion database consisting of 150 recordings from Vrancea subcrustal earthquakes. The evaluation is performed by using several goodness-of-fit parameters from the literature. Moreover, the applicability of the single-station sigma method is also investigated by using the same strong ground motion database recorded in 30 seismic stations from southern and eastern Romania. The influence of the soil conditions on the numerical results obtained in this study is investigated and discussed using the results provided by the analysis of variance method. The impact of the single-station standard deviation on the levels of seismic hazard is also assessed in this study, and the results show, in the analyzed cases, significant reductions in the hazard levels.

Authors:
Ioane D., Diaconescu M., Chitea F., Garbacea G.

Abstract:
In urban planning activities, besides a detailed seismic zonation, knowledge of the areal distribution of active faults, and particularly of faults crossing the city in heavily built districts, may be valuable in numerous cases. This chapter aims to identify active faults or fractures in Bucharest, a large city developed over thick layers of Quaternary unconsolidated sediments. To achieve this goal, the research is based on an integrated analysis of all existing relevant data coming from geology, geomorphology, geophysics and seismology. Another purpose is to understand the role of faults in the spatial variability of seismic damaging effects on buildings in view of a better future urban planning. The N-S fault system seems to be involved in neotectonics, affecting the geomorphology between Bucharest and Ploiesti cities. It could represent an active transcrustal fault, the deepest seismic event recorded within Bucharest at subcrustal depth being located on its southern prolongation. Within Bucharest the presence of faults affecting Pleistocene sediments was previously illustrated using borehole data, shallower vertical displacements of Quaternary formations along faults being interpreted in this study. The existing seismic reflection data recorded within Bucharest was used to interpret shallow faults considered as active or capable faults crossing Quaternary sedimentary deposits.