Abstract.A seismic hazard map proposed as part of a new building code for Romania is presented here on basis of the recommendations in EUROCODE 8.Seismic source zones within an area of about 200 km around Romania were constructed considering seismicity, neotectonics and geological development. The probabilistic seismic hazard assessment in terms of intensities is performed following Cornell (1968) with the program EQRISK (see Mc Guire, 1976), modified by us for use of intensities.To cope with the irregular isoseismals of the Vrancea intermediate depth earthquakes a factor is introduced to the attenuation law (Kövesligethy, 1907). Using detailed macroseismic maps of three earthquakes is calculated by fitting the attenuation law to observed intensities, i.e. to local ground conditions. Strong local variation of is avoided by a gridding of 0.5 • in longitude and 0.25 • in latitude. The contribution of the Vrancea intermediate depth zone to the seismic hazard at each grid point is computed with the corresponding representative . A seismogenic depth of 120 km is assumed.The final seismic hazard is the combination of both contributions, of zones with crustal earthquakes and of the Vrancea intermediate depth earthquakes zone. Calculations are done for a recurrence period of 95, 475 and 10 000 years. All maps show the dominating effects of the intermediate depth earthquakes in the Vrancea zone, also for the capital Bucharest.
Abstract.A seismic hazard map proposed as part of a new building code for Bulgaria is presented here on basis of the recommendations in EUROCODE 8.Seismic source zones within an area of about 200 km around Bulgaria were constructed considering seismicity, neotectonic and geological development. The most time consuming work was to establish a homogeneous earthquake catalogue out of different catalogues.The probabilistic seismic hazard assessment in terms of intensities is performed following Cornell (1968) with the program EQRISK (see McGuire, 1976), modified by us for use of intensities. To cope with the irregular isoseismals of the Vrancea intermediate depth earthquakes a special attenuation factor is introduced (Ardeleanu et al., 2005), using detailed macroseismic maps of three major earthquakes.The final seismic hazard is the combination of both contributions, of zones with crustal earthquakes and of the Vrancea intermediate depth earthquakes zone. Calculations are done for recurrence periods of 95, 475 and 10 000 years.
An international, interdisciplinary project, which 2 years ago deployed the largest dense seismic antenna ever in Europe, expects in the next 2 years to present important findings on the lithosphere and asthenosphere of a portion of the Trans‐European Suture Zone (TESZ). Final processing is currently under way of the data from the array of 120 seismographs along a 900‐km‐long by 100‐km‐wide strip from Gottingen, Germany, in the south, through Denmark, to Stockholm, Sweden in the north, across the northwestern part of the TESZ (Figure 1). Project Tor is a teleseismic tomography experiment with interdisciplinary data exploitation. It extends across the broad TESZ boundary between two markedly different lithospheric domains.These are (1) Proterozoic Europe, with Precambrian crust in Sweden and eastern Europe, and (2) Phanerozoic central Europe, with most of the crust influenced by the Caledonian and Variscan orogenies and only small areas of relic Precambrian crust. The project is designed to investigate the deep lithosphere traces of the broad‐scale geology of the TESZ area, including the Tornquist Zone, from which Project Tor has its name. It is part of EUROPROBE, a major Earth science program of the European Science Foundation, which is run by a regional committee of the International Lithosphere Program.
Abstract. Since 2007 Bulgaria and Romania are members of the European Union. All member states have to introduce the European earthquake building code EUROCODE 8 (EC 8) in the coming years. Therefore, new seismic hazard maps have to be calculated according to the recommendations in EC 8.Here the authors present a novel approach to compute such hazard maps. We prefer to use the macroseismic intensity as hazard parameter because of two reasons:-The irregular azimuthal attenuation pattern of the Vrancea intermediate depth earthquakes can be advantageously taken into account by using detailed macroseismic maps.-The intensity is directly related to the degree of damage and is the original information in the historical earthquake catalogues.The main base of our probabilistic analysis is the earthquake catalogue for SE-Europe (Shebalin et al., 1998) in combination with national and regional catalogues. Fore-and aftershocks were removed. Seismic source zones inside an area of about 200 km around Romania and Bulgaria were defined based on seismicity, neotectonics and geological development. For each seismic source the intensity-frequency relation was calculated and a maximum possible earthquake as well as a seismogenic depth was estimated. An appropriate attenuation law was assumed. To cope with the irregular isoseismals of the Vrancea intermediate depth earthquakes, a factor was included in the macroseismic attenuation law. Using detailed macroseismic maps of three strong intermediate depth earthquakes, was calculated for each observation. Strong local variations of are avoided by averaging The contributions of all seismic sources, the crustal normal depth source zones and the Vrancea intermediate depth zone, were summed up and the annual probability of exceedance was calculated. The contribution of the Vrancea intermediate depth zone to each grid point was computed with the corresponding representative of this point; a seismogenic depth of 120 km has been assumed.Each final seismic hazard map is a combination of two maps, the one for normal depth source zones and the one for the Vrancea intermediate depth zone. This is illustrated for a recurrence period of 475 years. Additional hazard maps were calculated for different recurrence periods.
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