Seismic hazard in Romania is dominated by the Vrancea intermediate-depth events. In the same time... more Seismic hazard in Romania is dominated by the Vrancea intermediate-depth events. In the same time, at local scale the hazard generated by the superficial sources can not be neglected. An important zone affected by crustal earthquakes is Fagaras-Campulung seismic area where at least once per century are reported effects of VIII+ and/or IX MSK. In order to mitigate the seismic risk of the vulnerable man-made structures (bridges, large dams), we are investigating the local effects at certain sites in this mountainous area. The aim of this paper is to evaluate the seismic effects induced in the local structure of the Fagaras-Campulung area. A complex geotectonic and physical-lithological analysis has been carried out for the area of interest, which has the geographical limits between 45.0 - 46.00 North latitude and 24.00 - 25.80 East longitude. Seismicity of the area is presented with a history of seismic activity, majority of events are 2-3 MW but there are also some greater ones (28 s...
The Vrancea seismic zone (VSZ), located in Romania, at the sharp bend of the southeast Carpathian... more The Vrancea seismic zone (VSZ), located in Romania, at the sharp bend of the southeast Carpathians, is an anomalous intraplate seismic nest releasing the largest strain in continental Europe. The last powerful earthquake in Vrancea occurred in 1977 causing significant damage to the densely populated cities in southeast Romania. The seismic infrastructure was underdeveloped at that time and the earthquake was not well recorded locally. Using ambient seismic noise recorded at modern broadband seismic stations around Vrancea in the year 2020, and the approximate moment tensor solutions of significant earthquakes Mw>6 since 1977, we reconstruct ground-motion waveforms recorded by modern seismometers decades after their occurrence. The virtual earthquake approach uses empirical Green’s functions from ambient noise cross correlations between pairs of seismic stations and adds the signatures of a model earthquake: double couple mechanism, buried source, and a realistic earth model in th...
The Vrancea seismogenic zone denotes a peculiar source of seismic hazard which represents a major... more 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 su...
The seismic response of the ground motion is analysed using processed recordings and related spec... more The seismic response of the ground motion is analysed using processed recordings and related spectral characteristics. The analysis is carried out for few representative different sites, with different geological local conditions. Data used are recordings from the last strongest seismic events (1986, August 30, Mw = 7.1, 1990, May 30, Mw = 6.9 and 1990, May 31, Mw=6.4). The approach used herein to assess the particular features of the seismic effects could open a new perspective in microzoning and risk studies. In the context of Vrancea-intermediate depth seismicity, whose effects are encountered at long epicentral distances, the choice of these sites is fully justified. Therefore the paper intends to focus on the particularities in the site effects that occur due to the sedimentary deposits’ oscillation under strong seismic ground motion for different areas. The spectral amplification factors are introduced in order to have a quantitative representation with respect to the variabil...
In this paper we highlight the capabilities and advantages of GIS, through an explicit analysis o... more 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.
In this study, we mapped the depth of the fundamental frequency of resonance for the Moldavian an... more In this study, we mapped the depth of the fundamental frequency of resonance for the Moldavian and Scythian Platforms using the available data at 18 seismic stations. Each site was investigated through the computation of H/V spectral ratios from three-component single station measurements of ambient vibrations. The observed resonance peaks were interpreted according with the available geological information.
A newly compiled high-quality ground-shaking dataset of 207 intermediate-depth earthquakes record... more A newly compiled high-quality ground-shaking dataset of 207 intermediate-depth earthquakes recorded in the Vrancea region of the south-eastern Carpathian mountains in Romania was used to develop region-specific empirical predictive equations for various intensity measures: peak ground acceleration, peak ground velocity, and 5%-damped pseudo-spectral acceleration up to 10 s. Besides common predictor variables (e.g. moment magnitude, depth, hypocentral distance, and site conditions), additional distance scaling parameters were added to describe the specific attenuation pattern observed at the stations located not only on the back and fore but also along the Carpathian arc. In this model, we introduce a proxy measure for the site as the fundamental frequency of resonance to characterize the site response at each recording seismic station beside the soil classes. To additionally reduce the site-to-site variability, a non-ergodic methodology was considered, resulting in a lower standard ...
Seismic hazard in Romania is dominated by the Vrancea intermediate-depth events. In the same time... more Seismic hazard in Romania is dominated by the Vrancea intermediate-depth events. In the same time, at local scale the hazard generated by the superficial sources can not be neglected. An important zone affected by crustal earthquakes is Fagaras-Campulung seismic area where at least once per century are reported effects of VIII+ and/or IX MSK. In order to mitigate the seismic risk of the vulnerable man-made structures (bridges, large dams), we are investigating the local effects at certain sites in this mountainous area. The aim of this paper is to evaluate the seismic effects induced in the local structure of the Fagaras-Campulung area. A complex geotectonic and physical-lithological analysis has been carried out for the area of interest, which has the geographical limits between 45.0 - 46.00 North latitude and 24.00 - 25.80 East longitude. Seismicity of the area is presented with a history of seismic activity, majority of events are 2-3 MW but there are also some greater ones (28 s...
The Vrancea seismic zone (VSZ), located in Romania, at the sharp bend of the southeast Carpathian... more The Vrancea seismic zone (VSZ), located in Romania, at the sharp bend of the southeast Carpathians, is an anomalous intraplate seismic nest releasing the largest strain in continental Europe. The last powerful earthquake in Vrancea occurred in 1977 causing significant damage to the densely populated cities in southeast Romania. The seismic infrastructure was underdeveloped at that time and the earthquake was not well recorded locally. Using ambient seismic noise recorded at modern broadband seismic stations around Vrancea in the year 2020, and the approximate moment tensor solutions of significant earthquakes Mw>6 since 1977, we reconstruct ground-motion waveforms recorded by modern seismometers decades after their occurrence. The virtual earthquake approach uses empirical Green’s functions from ambient noise cross correlations between pairs of seismic stations and adds the signatures of a model earthquake: double couple mechanism, buried source, and a realistic earth model in th...
The Vrancea seismogenic zone denotes a peculiar source of seismic hazard which represents a major... more 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 su...
The seismic response of the ground motion is analysed using processed recordings and related spec... more The seismic response of the ground motion is analysed using processed recordings and related spectral characteristics. The analysis is carried out for few representative different sites, with different geological local conditions. Data used are recordings from the last strongest seismic events (1986, August 30, Mw = 7.1, 1990, May 30, Mw = 6.9 and 1990, May 31, Mw=6.4). The approach used herein to assess the particular features of the seismic effects could open a new perspective in microzoning and risk studies. In the context of Vrancea-intermediate depth seismicity, whose effects are encountered at long epicentral distances, the choice of these sites is fully justified. Therefore the paper intends to focus on the particularities in the site effects that occur due to the sedimentary deposits’ oscillation under strong seismic ground motion for different areas. The spectral amplification factors are introduced in order to have a quantitative representation with respect to the variabil...
In this paper we highlight the capabilities and advantages of GIS, through an explicit analysis o... more 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.
In this study, we mapped the depth of the fundamental frequency of resonance for the Moldavian an... more In this study, we mapped the depth of the fundamental frequency of resonance for the Moldavian and Scythian Platforms using the available data at 18 seismic stations. Each site was investigated through the computation of H/V spectral ratios from three-component single station measurements of ambient vibrations. The observed resonance peaks were interpreted according with the available geological information.
A newly compiled high-quality ground-shaking dataset of 207 intermediate-depth earthquakes record... more A newly compiled high-quality ground-shaking dataset of 207 intermediate-depth earthquakes recorded in the Vrancea region of the south-eastern Carpathian mountains in Romania was used to develop region-specific empirical predictive equations for various intensity measures: peak ground acceleration, peak ground velocity, and 5%-damped pseudo-spectral acceleration up to 10 s. Besides common predictor variables (e.g. moment magnitude, depth, hypocentral distance, and site conditions), additional distance scaling parameters were added to describe the specific attenuation pattern observed at the stations located not only on the back and fore but also along the Carpathian arc. In this model, we introduce a proxy measure for the site as the fundamental frequency of resonance to characterize the site response at each recording seismic station beside the soil classes. To additionally reduce the site-to-site variability, a non-ergodic methodology was considered, resulting in a lower standard ...
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