Probabilistic seismic hazard assessment of Kishanganj, Bihar, India

Kishanganj is the easternmost district in the Indian state of Bihar, which shares its international border with Nepal to the north and state border with West Bengal to the east. It is one of the most important trading hubs in the eastern Bihar region because of its closeness to the Nepal border. Kishanganj is situated close to the Indo-Eurasian thrust zone and has been affected by several devastating earthquakes in the past. Hence, it is indispensable to perform probabilistic seismic hazard analysis for the Kishanganj district. An earthquake catalogue of the past 300 yrs, consisting of earthquake events within a radius of 500 km from the center of Kishanganj, is considered for the estimation of bedrock level peak ground acceleration (PGA) values at 2% and 10% probability of exceedance in 50 yrs. Due to the absence of region-specific ground motion prediction equations (GMPEs), a logic-tree based approach consisting of four GMPEs is considered which resulted in a maximum expected PGAs of 0.39 and 0.17 g at 2% and 10% probability of exceedance in 50 yrs. Our results from seismic hazard maps reveal that the southern parts of the Kishanganj district and some eastern parts such as Pothia are most vulnerable to seismic hazard as they have high expected PGA values ranging between 0.36 and 0.39 g as per the MCE condition. Kishanganj district headquarter, i.e., Kishanganj city (0.33-0.39 g) and Kochadhamin (0.33-0.39 g) are found most vulnerable to seismic hazard while Terhagachh (0.28-0.31 g), Dighabank (0.30-0.29 g) and Thakurganj (0.25-0.35 g) are found to be least vulnerable.