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