A near-fault probabilistic seismic hazard assessment for Yasouj, located in the Kazerun fault system, southwest Iran

Abstract

The Kazerun fault system (KFS) is located in the central part of the Zagros, the most seismically active orogenic belt in the Iranian plateau. The city of Yasouj is located in the midst of the KFS and thus exposed to high earthquake hazard. In this study, we conduct a probabilistic seismic hazard analysis (PSHA) which includes near-fault effects. For this purpose, different ground motion prediction equations (GMPEs) are ranked using the deviance information criterion (DIC) data-driven method against a dataset of the regional recorded strong motions. Then, the most appropriate GMPEs are selected for use in a logic tree framework to consider the epistemic uncertainty. In addition, the shear wave velocity is estimated using experimental data and the local site conditions are evaluated for different parts of the city. In addition, the seismicity parameters are obtained using the maximum likelihood methodology considering the magnitude uncertainty. The results show large variations in the spectral accelerations among different locations at short oscillator periods, while no significant difference is observed at longer periods. Moreover, due to the local site conditions, the highest ground motions are expected in the northeastern part of the Yasouj city. Comparing the results of this study with the Iranian seismic code design spectra shows that the design spectra of the Iranian seismic code are underestimating the ground motions at short spectral periods. The results of this study can be useful for both engineers and decision-makers to reduce earthquake risk for the region under study.