

The study of site effects and the microzonation of a part of metropolitan Sofia, based on the modelling of seismic ground motion along three cross sections are performed. Realistic synthetic strong motion waveforms are computed for scenario earthquakes (M = 7) applying a hybrid modelling method, based on the modal summation technique and finite differences scheme. The synthesised ground motion time histories are source and site specific. The site amplification is determined in terms of response spectra ratio (RSR). A suite of time histories and quantities of earthquake engineering interest are provided. The results of this study constitute a database that describes the ground shaking of the urban area. Using this database, the problem of estimation of seismic wave's behaviour for the Sofia region is discussed. We employed synthetic velocigrams to extract maximum particle velocities distribution has to calculate horizontal strain factor Log10ε distribution, using simplified relation between particle velocity and velocity of shear waves in the surface layer. It is shown that it is possible to estimate liquefaction susceptibility in terms of standard penetration values and initial overburden stress. The results can be used for microzonation purposes as well for determination main parameters of structural control devices in the Sofia region.