Probabilistic Seismic Hazard Analysis for Offshore Bangladesh Including Fault Sources

Abstract

This paper presents a probabilistic seismic hazard analysis (PSHA) for a site offshore Maheshkhali Island, Bangladesh. The tectonic setting of the area is complex, and the PSHA includes active crustal faults, megathrust and intraplate subduction faults, and a background gridded seismicity areal source zone based on historical and recorded earthquakes. In addition, we model several rupture scenarios for the closest megathrust source. The peak ground acceleration values for return periods of 475 years and 2475 years are 0.33 g and 0.63 g, respectively. These values are higher than previous studies conducted in the area, however, past studies only included areal source zones based on recorded seismicity whereas this study takes advantage of recent research to include more detailed fault data. The deaggregation plots show that the main contributors to the hazard are a magnitude 6.5–7.1 earthquake 15–20 km from the site on the Maheshkhali fault and a magnitude 8.0–8.8 earthquake 120–250 km from the site on the Ramree megathrust.