Seismic hazard assessment of the Shillong Plateau using a probabilistic approach

Abstract

Seismotectonic processes of the Shillong Plateau (SP) have been influenced by the Himalayan orogeny, the India-Burmese subduction, and the Bengal Basin evolution leading to high seismic activity in the region. With a goal of assessing seismic hazards in the SP and providing a scientific information to engineering and disaster risk management communities, a probabilistic seismic hazard analysis is employed to determine hazard in highly-populated districts of SP and particularly in Shillong, Nongpoh, and Tura cities, located within the districts. This analysis is based on the use of historical and instrumentally recorded regional earthquakes since 1411 and deals with uncertainties related to earthquake magnitudes, rupture locations, and the frequency of ground motion exceedance. Individual hazard curves indicate that the Barapani fault possesses the highest frequency of seismic hazard for Shillong city and Nongpoh, and the Eocene hinge zone and Dauki faults are responsible for the highest frequency of seismic hazard at Tura. The results of the hazard assessment together with those obtained earlier using a scenario-based approach demonstrate that although the Oldham fault located near Tura can produce a great, but rare earthquake, few other nearby faults are capable of producing smaller magnitude events with a higher probability of occurrence.