This paper describes the outcome of the advanced seismic hazard and seismic risk estimates recently performed for the city of Sofia, based on the state-of-the-art of knowledge for this site. Some major results of the neo-deterministic, scenario-based, seismic hazard assessment approach (NDSHA) to the earthquake hazard assessment for the city of Sofia are considered. Further validations of the recently constructed synthetic strong motion database, containing site and seismic source-specific ground motion time histories are performed and discussed. Displacement and acceleration response spectra are considered. The elastic displacement response spectra and displacement demand are discussed with regard to earthquake magnitude, seismic source-to-site distance, seismic source mechanism, and local geological site conditions. The elastic response design spectrum from the standard pseudo-acceleration, versus natural period, T n , format, converted to a capacity diagram in S a -S d format is discussed in the perspective of the Eurocode 8 provisions. A brief overview of the engineering applications of the seismic demand obtained making use of the NDSHA is supplied. Some applications of the outcome of NDSHA procedure for engineering purposes are shown. The obtained database of ground shaking waveforms and time-histories, computed for city of Sofia is used to: (1) extract maximum particle velocities; (2) calculate the space distribution of the horizontal strain factor Log 10 e; (3) estimate liquefaction susceptibility in terms of standard penetration test, N values, and initial over burden stress; (4) estimate damage index distribution; and (5) map the distribution of the expected pipe breaks and red-tagged buildings for given scenario earthquakes, etc. The theoretically obtained database, based on the simultaneous treatment of the data from many disciplines, contains data fully suitable for practical use. The proper use of this database can lead to a significant seismic vulnerability reduction and thus contributes to earthquake preparedness.

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Strong shallow and intermediate-depth scenario earthquakes for two major cites in Bulgaria are discussed. The contribution of the earthquake source and the local site geology to the seismic input is illustrated. Due to the lack of strong motion records a neo-deterministic seismic hazard assessment procedure is used to generate synthetic seismic signals. After some parametric analyses the computed signals are validated against the few available data. Prognostic estimates of the dynamic coefficient for the target sites are performed with respect to the defined scenario earthquakes and local site models, corresponding to the Eurocode 8 ground types A, B and C. The obtained results show that: (1) the seismic source influence on the seismic input at a given site is comparable with that of the local site geology; (2) the dynamic coefficients, computed for accelerograms (observed and computed) due to strong intermediate-depth Vrancea earthquakes overestimate significantly the values recommended by the Eurocode 8 (EC8) for periods T > 1s.

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