Probabilistic Seismic Hazard Assessment of Sitamarhi near the Central Himalayan Region

Sitamarhi, situated in the North-Bihar region of the Himalayan foothills is one of the seismically vulnerable regions of India. This region faced several devastating earthquakes, such as the 1934 and 1988 Bihar Nepal earthquake and the 2015 Nepal earthquake due to the movement of tectonic plates. The purpose of the present study is to exhibit the uniform hazard spectrum (UHS) and peak ground acceleration (PGA) values based on the probabilistic seismic hazard method using different seismotectonic parameters. The Gutenberg Richter (G-R) seismicity parameters ‘a’ and ‘b’ were estimated on the basis of regional earthquake magnitude data for the studied region. Regional earthquakes data were taken from the United States Geological Survey (USGS), International Seismological Centre (ISC), Indian Meteorological Department (IMD), and Seismotectonic Atlas of India. The region of interest for the probabilistic seismic hazard analysis (PSHA) is within a 500 km radius considering past seismicity and 62 seismotectonic sources which were identified in the study area. Large-scale geological features were utilised to describe the regional seismic source zones, which were used to derive the relationship between return period and ground motion parameters. Estimated PGA values are 0.92g for 2% and 0.68g for 10% probability of exceedance in 50 years time period, respectively. This research infer that the West Patna fault (WPF) and Sitamarhi fault (SMF) are the two maximum contributors in PGA for the Sitamarhi region.