Probabilistic seismic hazard analysis for Nepal

Abstract

Nepal lies in the zone of Himalayan belt formed due to collision of two continental plates and have the high probability of earthquake occurrence. Many destructive earthquakes have been reported in past causing the massive destruction of lives and property. For reducing the risks caused by seismic events, proper study should be carried out beforehand, one of which is seismic hazard analysis. In this study, Probabilistic Seismic Hazard Analysis (PSHA) is carried out for Nepal and the hazard map is prepared in terms of Peak Horizontal Acceleration (PHA) for 500 years return period at bedrock level. The available earthquake catalogue for Nepal is processed for magnitude homogeneity and removal of aftershocks. The seismicity parameters are obtained using the method obtained for multiple catalogs with different level of completeness. The area source models are used for the analysis since the earthquake distribution is diffused and no particular information on faults is available. The attenuation relationship available for subduction zone earthquake is used for determining the PHA at a particular site. The software CRISIS2007 is used for computing and preparing hazard map for Nepal. The map is divided into number of sites using grids of 0.1o by 0.1o and PHA value at each grid is computed, finally, obtaining the hazard map for Nepal. The hazard map shows that the PHA value varies from 0.09g to 0.5g for Nepal, with the maximum values at Eastern and Western part of Nepal. This high level of seismicity in the regions shows that the proper plans should be implemented for reducing the risks caused by seismic events, like earthquake resistant design of structures.