SEISMIC RISK OF THE TOWN OF PROVADIA

A multidisciplinary approach including seismotectonic, geological and geophysical studies, generation of synthetic accelerograms, seismic hazard assessment has been adopted. The study discusses the historic seismicity of Bulgaria used to define earthquake zones and it also reviews the availbie attenuation laws and scaling equations for Intensities and Fourier spectra. The probabilistic hazard assessment of strong earthquake ground motion in the vicinity of the town of Provadia, Bulgaria, for two main models and six submodels is presented. The ground motion predictions are in terms of Fourier amplitude spectra for ۵۰ years exposure for periods ۰,۰۴ to ۷.۵s, probabilities of nonexceedance p=۰.۰۱,۰_۱,۰_۵,۰.۹ and ۰.۹۹. The results show that the uniform hazard spectra at Provadia are significantly affected by the choice of Vrancea earthquakes attenuation. If the small attenuation from the deep earthquakes in this zone is neglected, the predicted motions are underestimated