DETERMINISTIC EARTHQUAKE SCENARIO FOR THE CITY OF SOFIA.

In the present study a set of two deterministic earthquake scenarios (expressed in peak ground acceleration and macroseismic intensity MSK) are generated for the city of Sofia - the capital of Bulgaria. The study is guided by the perception that usable and realistic, based on both local seismic history and tectonic setting, ground motion maps to be produced for urban area. The city is situated in the center of the Sofia area that is the most populated (the population is of more than 1.2 mil. inhabitants), industrial and cultural region of Bulgaria that faces considerable earthquake risk. The contemporary tectonic activity of the Sofia area is predominantly associated with marginal faults of Sofia graben. In the study the local ground shaking levels are computed using the six ground-motion models selected (GMPE's) for tectonically active regions. The scenario maps account for soil amplification effects using the geotechnical zonation of the considered urban area. Two scenario earthquakes are considered: earthquake with magnitudes MW6.5 occurred at the active fault located south of the city of Sofia (along the northern margin of the Vitosha Mountain) and MW7.0 quake (occurred at the fault located northern of the city). The MW6.5 event is the "true" historical 1858 earthquake with the strongest seismic impact on the city of Sofia. The assessment of seismic hazard and generation of earthquake scenarios is the first link in the prevention chain and the first step in the evaluation of the seismic risk. The implementation of the earthquake scenarios into the policies for seismic risk reduction will allow focusing on the prevention of earthquake effects rather than on intervention following the disasters. [ABSTRACT FROM AUTHOR]