Generation of Probabilistic Seismic Hazard Map of Assam State

Assam state is located in highest seismic zone of India. In this paper, an attempt is made to generate hazard map of the Assam state considering updated earthquake catalogue till 2021. A systematic probabilistic seismic hazard assessment (PSHA) is carried out to evaluate seismic hazard map of Assam. The study area is divided into nine areal zones based on seismotectonics and geology of the area. The earthquake recurrence parameters are obtained from the magnitude frequency relationships for each zone. A mixed kind of seismotectonics is observed such as continental crust region, subduction zone, and intraplate region. Depending upon the seismotectonic of the study area, eight different attenuation relationships are used. The logic tree approach is used to minimize epistemic uncertainty and thus obtain the hazard curves. A hazard map of Assam state is prepared and presented in the paper. The peak ground acceleration value at the rock outcrop of the Assam region for return period of 500 yrs. and 2500 yrs. varies between 0.1 g to 0.2 g and 0.22 g to 0.42 g, respectively. Rock-level response spectra are proposed for Guwahati City and Dispur City. The above spectra can be used for design purpose.