We present a refined and the most complete catalogue of the focal mechanisms for the Intra-Carpat... more We present a refined and the most complete catalogue of the focal mechanisms for the Intra-Carpathian region of Romania. It contains the high-quality solutions computed for 1217 earthquakes recorded between 1909 and 2018. Primary data gathered from the original seismograms and seismic bulletins have been used to compute the source parameters and focal mechanisms solutions. The focal mechanisms have been obtained using the HASH method by the polarities and S/P amplitudes ratios inversion. Our catalogue provides data necessary for the investigation of the contemporary stress field at different scales with high spatial and temporal resolution. We determined the stress field characteristics through formal inversion of focal mechanisms and also computed the reactivation potential of the active fault systems using the Win‑Tensor program. The stress field is heterogeneous, with SHmax significantly deviating from the first-order stress field direction and also with strong local variations i...
EGU General Assembly Conference Abstracts, Apr 1, 2016
Between 19 July and 05 August 2015, a seismic sequence occurred at the border region between the ... more Between 19 July and 05 August 2015, a seismic sequence occurred at the border region between the northwestern part of Romania and Ukraine. The most significant event of 3.8 ML occurred on 19 July at a depth of 4.6 km. The sequence is the most significant seismic activity instrumentally recorded in the northwestern part of Romania, a region generally characterized by low seismic activity. The location results, obtained by JHD and HYPO-DD techniques, show a NE-SW alignment along the Faget Fault. The focal depth estimation reveals a variation in depth delimiting two fault segments: one above 4 km depth, the other below 6 km depth. The hypocenter clustering is attributed to a non-breakable structure between the two segments. The fault plane solutions obtained using the first P-wave polarities and waveform inversion consistently show a strike-slip fault plane solution.
In this paper, we have studied the seismic activity in relation with geology, and tectonics in or... more In this paper, we have studied the seismic activity in relation with geology, and tectonics in order to highlight seismogenic processes recorded in Danubian area and Hateg-Strei Basin. The Danubian seismogene area presents a complex geological structure, being characterized by the following tectonic units: Median Dacides (Getic and Supra-Getic nappes), Marginal Dacides (Danubian Unit) and External Dacides (Severin nappe). The recent seismic activity in this area, starting from 1990 until present, is described by the seismic sequence from 2002, in the Moldova Noua area, in connection to Oravita-Moldova Noua fault and by the seismic sequence from 1991, in the Baile Herculane area, belonging to the Cerna-Jiu fault system. Also, the Teregova area is present with the seismic sequence from 2014 and another two smaller sequences. From a statistical point of view, the seismicity is mainly described by the b-value coefficients from the empirical relation between the frequencies and magnitude...
Springer International Publishing AG, part of Springer Nature 2018 R. Vacareanu and C. Ionescu (eds.), Seismic Hazard and Risk Assessment, Springer Natural Hazards, 2018
The study region is the most important seismic region of Romania when we refer to the crustal sei... more 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 a significant effect on 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 recent earthquakes and focal mechanisms catalogues basis. This model was elaborated starting from the relationship between geology and historical and instrumental seismicity. Then it was better constrained by geophysical, neotectonic, and 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 mechanism's solutions.
We analyze the seismic activity recorded between January and March 2012 near the city of Timisoar... more We analyze the seismic activity recorded between January and March 2012 near the city of Timisoara. We identified two earthquake sequences during this time interval: one started on 07.01.2012 at a few kilometers SW of the city (N = 3 events, Depic = 1-7 km, Mwmin = 2.1, Mwmax = 3.1, hmin = 7.1±1.6 km, hmax = 9.8±1.0 km), the other with the main event on 09.01.2012 located at 30 km East of the city (N = 20 events, Mwmin = 0.4, Mwmax = 3.4, hmin = 2±2.6 km, hmax = 14.5±1.7 km). Epicentral zones of these sequences have elongated shapes and develop along a major fault system of the region, particularly at its intersection with other deeply fractured structures. The depth distribution displays three small groups of earthquakes at 2-5 km, 5-11 km and 11-16 km, respectively. Focal mechanism solutions estimated for the main events of the sequence show possible causative faults EW to ENE-WSW oriented, consistent with seismicity, geology, local stress field and seismotectonics.
has been achieved. This paper refers to the essential characteristics of the first component of t... more has been achieved. This paper refers to the essential characteristics of the first component of this database, namely the Parametric Earthquakes Catalogue for the Banat Seismic Region (PECBSR). PECBSR comprises 7783 crustal earthquakes
IOP Conference Series: Earth and Environmental Science, 2019
The purpose of the present study is to elaborate a new model of the macroseismic intensity attenu... more 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
The macroseismic effects of three major events recorded in historical time (1738, 1802, 1838) are... more 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.
Timisoara is a great Romanian town (about four thousands people) placed in the Western Plain of R... more Timisoara is a great Romanian town (about four thousands people) placed in the Western Plain of Romania, on the southeastern border of Pannonian Basin. The seismicity of the region is moderate, with strong but rare earthquakes (Mmax = 6.5, Imax observed = 9 MSK degrees - for 1440 2001 period). For Timisoara city, maximum expected intensity is 7.5 degrees from two main sources: Timisoara (the western part of the town) or Sag (at 15 km to South-West). There are several sources to the North and East near the city which have maximum 6 MSK degrees. Superficial geology in the town and surroundings consists in Quaternary unconsolided sediments which lie over the Miocen Pliocen molasses with about 1700 m of sandstones, marls,clays, sands and gravels. Geotechnical investigations (drillings) made possible a zoning which concerns three main zones: sands, clays and sandy clays or sands with clay. There are more sites with thick anthropic debris fillings. The underground water level is very high (1 - 4 meters). The town is crossed by Bega river from West to East. In 1991, several accelerograms were obtained in Timisoara, from local earthquakes (Ms = 5.5) occurred at about 40 km SW from the city. These show periods of 0.2 0.3 seconds. The maximum intensities recorded in Timisoara were 5.5 MSK degrees. In order to obtain more information about local soil effects Nakamura`s method is used. Noise measurements for 23 sites were performed using a velocimeter with longitudinal component oriented to North. Generally, the H/V ratios are fairly flat, without distinct picks, posible because of the small impedance contrasts in the subsoil. It is posible that this kind of ratio to reflects a stiff soil. When it is possible, the greatest picks correspond to a large frequency range: 1.4 9.7 Hz. There are a good to medium correlation between macroseismic observation in the city, periods of the accelerograms and the predominant frequencies as result from noise analysis. A strong lateral variation was observed in the frequency band, thus more measurement points are necessary for a mapping of resonant frequency.
We present a refined and the most complete catalogue of the focal mechanisms for the Intra-Carpat... more We present a refined and the most complete catalogue of the focal mechanisms for the Intra-Carpathian region of Romania. It contains the high-quality solutions computed for 1217 earthquakes recorded between 1909 and 2018. Primary data gathered from the original seismograms and seismic bulletins have been used to compute the source parameters and focal mechanisms solutions. The focal mechanisms have been obtained using the HASH method by the polarities and S/P amplitudes ratios inversion. Our catalogue provides data necessary for the investigation of the contemporary stress field at different scales with high spatial and temporal resolution. We determined the stress field characteristics through formal inversion of focal mechanisms and also computed the reactivation potential of the active fault systems using the Win‑Tensor program. The stress field is heterogeneous, with SHmax significantly deviating from the first-order stress field direction and also with strong local variations i...
EGU General Assembly Conference Abstracts, Apr 1, 2016
Between 19 July and 05 August 2015, a seismic sequence occurred at the border region between the ... more Between 19 July and 05 August 2015, a seismic sequence occurred at the border region between the northwestern part of Romania and Ukraine. The most significant event of 3.8 ML occurred on 19 July at a depth of 4.6 km. The sequence is the most significant seismic activity instrumentally recorded in the northwestern part of Romania, a region generally characterized by low seismic activity. The location results, obtained by JHD and HYPO-DD techniques, show a NE-SW alignment along the Faget Fault. The focal depth estimation reveals a variation in depth delimiting two fault segments: one above 4 km depth, the other below 6 km depth. The hypocenter clustering is attributed to a non-breakable structure between the two segments. The fault plane solutions obtained using the first P-wave polarities and waveform inversion consistently show a strike-slip fault plane solution.
In this paper, we have studied the seismic activity in relation with geology, and tectonics in or... more In this paper, we have studied the seismic activity in relation with geology, and tectonics in order to highlight seismogenic processes recorded in Danubian area and Hateg-Strei Basin. The Danubian seismogene area presents a complex geological structure, being characterized by the following tectonic units: Median Dacides (Getic and Supra-Getic nappes), Marginal Dacides (Danubian Unit) and External Dacides (Severin nappe). The recent seismic activity in this area, starting from 1990 until present, is described by the seismic sequence from 2002, in the Moldova Noua area, in connection to Oravita-Moldova Noua fault and by the seismic sequence from 1991, in the Baile Herculane area, belonging to the Cerna-Jiu fault system. Also, the Teregova area is present with the seismic sequence from 2014 and another two smaller sequences. From a statistical point of view, the seismicity is mainly described by the b-value coefficients from the empirical relation between the frequencies and magnitude...
Springer International Publishing AG, part of Springer Nature 2018 R. Vacareanu and C. Ionescu (eds.), Seismic Hazard and Risk Assessment, Springer Natural Hazards, 2018
The study region is the most important seismic region of Romania when we refer to the crustal sei... more 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 a significant effect on 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 recent earthquakes and focal mechanisms catalogues basis. This model was elaborated starting from the relationship between geology and historical and instrumental seismicity. Then it was better constrained by geophysical, neotectonic, and 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 mechanism's solutions.
We analyze the seismic activity recorded between January and March 2012 near the city of Timisoar... more We analyze the seismic activity recorded between January and March 2012 near the city of Timisoara. We identified two earthquake sequences during this time interval: one started on 07.01.2012 at a few kilometers SW of the city (N = 3 events, Depic = 1-7 km, Mwmin = 2.1, Mwmax = 3.1, hmin = 7.1±1.6 km, hmax = 9.8±1.0 km), the other with the main event on 09.01.2012 located at 30 km East of the city (N = 20 events, Mwmin = 0.4, Mwmax = 3.4, hmin = 2±2.6 km, hmax = 14.5±1.7 km). Epicentral zones of these sequences have elongated shapes and develop along a major fault system of the region, particularly at its intersection with other deeply fractured structures. The depth distribution displays three small groups of earthquakes at 2-5 km, 5-11 km and 11-16 km, respectively. Focal mechanism solutions estimated for the main events of the sequence show possible causative faults EW to ENE-WSW oriented, consistent with seismicity, geology, local stress field and seismotectonics.
has been achieved. This paper refers to the essential characteristics of the first component of t... more has been achieved. This paper refers to the essential characteristics of the first component of this database, namely the Parametric Earthquakes Catalogue for the Banat Seismic Region (PECBSR). PECBSR comprises 7783 crustal earthquakes
IOP Conference Series: Earth and Environmental Science, 2019
The purpose of the present study is to elaborate a new model of the macroseismic intensity attenu... more 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
The macroseismic effects of three major events recorded in historical time (1738, 1802, 1838) are... more 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.
Timisoara is a great Romanian town (about four thousands people) placed in the Western Plain of R... more Timisoara is a great Romanian town (about four thousands people) placed in the Western Plain of Romania, on the southeastern border of Pannonian Basin. The seismicity of the region is moderate, with strong but rare earthquakes (Mmax = 6.5, Imax observed = 9 MSK degrees - for 1440 2001 period). For Timisoara city, maximum expected intensity is 7.5 degrees from two main sources: Timisoara (the western part of the town) or Sag (at 15 km to South-West). There are several sources to the North and East near the city which have maximum 6 MSK degrees. Superficial geology in the town and surroundings consists in Quaternary unconsolided sediments which lie over the Miocen Pliocen molasses with about 1700 m of sandstones, marls,clays, sands and gravels. Geotechnical investigations (drillings) made possible a zoning which concerns three main zones: sands, clays and sandy clays or sands with clay. There are more sites with thick anthropic debris fillings. The underground water level is very high (1 - 4 meters). The town is crossed by Bega river from West to East. In 1991, several accelerograms were obtained in Timisoara, from local earthquakes (Ms = 5.5) occurred at about 40 km SW from the city. These show periods of 0.2 0.3 seconds. The maximum intensities recorded in Timisoara were 5.5 MSK degrees. In order to obtain more information about local soil effects Nakamura`s method is used. Noise measurements for 23 sites were performed using a velocimeter with longitudinal component oriented to North. Generally, the H/V ratios are fairly flat, without distinct picks, posible because of the small impedance contrasts in the subsoil. It is posible that this kind of ratio to reflects a stiff soil. When it is possible, the greatest picks correspond to a large frequency range: 1.4 9.7 Hz. There are a good to medium correlation between macroseismic observation in the city, periods of the accelerograms and the predominant frequencies as result from noise analysis. A strong lateral variation was observed in the frequency band, thus more measurement points are necessary for a mapping of resonant frequency.
Cartea reprezinta teza de doctorat a autorului sustinuta in sedinta publica in martie 2011 la Fac... more Cartea reprezinta teza de doctorat a autorului sustinuta in sedinta publica in martie 2011 la Facultatea de Fizica din Bucuresti
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