Probabilistic Assessment of PGA and UHS for Bojnurd city, the Capital of North Khorasan Province, Iran

Probabilistic seismic hazard assessment (PSHA) of horizontal peak ground acceleration (PGA) and Uniform Hazard Spectra (UHS) on bedrock for different hazard levels is conducted in this study for Bojnurd city, the capital of North Khorasan province, Iran. Therefore, all historical and instrumental earthquakes in a radius of 200 km of the center of Bojnurd city are gathered and after elimination of the aftershocks and foreshocks, the main earthquakes are identified in order to calculate the seismic parameters by Kijko (2000) method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. Bojnurd city and its vicinity are meshed by 8 vertical and 11 horizontal lines. PGAs and UHS are calculated for all 88 points of the mesh using the logic tree method and different attenuation relationships with different weighted coefficients. These calculations are performed for two hazard levels of 10% and 2% probability of being exceeded in 50 years (hazard levels 1 and 2 respectively). Regional seismic hazard maps for PGAs and UHS for different locations of Bojnurd city and its vicinity are provided.