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The PSHA for the Western Balkan Countries builds upon extensive research and database compilation carried out over the last three years by the institutions participating in the BSHAP project. Within the frame of BSHAP, it has been impossible to provide all the relevant information, even for the faults that have generated strongest earthquakes with Mw>6.5 in the region. Seismic hazard assessment was accomplished using the smoothed gridded seismicity methodology. This method defines voluminous character of seismicity within a ‘source zone’ and determines it as a spatial unit of the seismically active Earth crust. This unit can be approximated by a unified seismic regime. The seismic sources of the region modeled during BSHAP are given in Figure 2. Hazard calculations were accomplished using the OHAZ 6.0 software, a joint development of Environmental Agency of the Republic of Slovenia and the Institute of Geosciences of Albania, which was greatly improved for the BSHAP project. The seismic hazard maps were obtained by interpolation of the mean hazard curves at specified annual frequency of exceedance. Seismic hazard maps for peak ground acceleration (PGA) corresponding to 10% probability of exceedance in 10 years (95- years return period) and 10% probability of exceedance in 50 years (475-years return period) were calculated. Figure 5 shows the seismic hazard map for PGA on uniform firm rock site conditions (average 800m/s shear-wave velocity in the upper 30 m of the crust) at 10% probability of exceedance in 50 years, corresponding to the 475-years return period. The seismic hazard maps derived for BSHAP provide a good basis to characterize the seismic hazard in the region. These maps should be improved, based on the experience from BSHAP project, in terms of seismic source characterization, ground motion prediction equations and seismic hazard assessment methodology.

 

Seismic hazard map for PGA on uniform firm rock site conditions at 10% probability of exceedance in 50 years developed during BSHAP