CHARACTERISTICS OF SEISMICITY, TECTONICS AND SEISMIC HAZARD ASSESSMENT OF ASSAM

Abstract

Assam is a state in northeast India which lies at 24º 8' N to 28º 2' N Latitude and 89º-96º E Longitude is a seismically active region with major seismic faults. The largest earthquake that has occurred in Assam during the past 100 years is the Assam-Tibet earthquake in the year 1950 which is also known as the Assam earthquake of magnitude Mw=8.6. It is also the largest earthquake caused by two continental plates colliding. Using the Gumbel method, the Gumbel parameters are also calculated, and the yearly expected number, return period, probability of occurrence, and probability of recurrence for different time periods are reported. Seismic hazard analysis is the valued estimation of ground-shaking hazards at a particular region or area. This study also calculates seismic hazards by the probabilistic seismic hazard analysis (PSHA) using Crisis 2020 software. For this purpose whole area has been divided into four zones on the basisof seismotectonic and geomorphic areas for calculation of seismic hazard, earthquake catalogues from 1900-2022 are prepared and their homogeneity and completeness are checked. The hazard parameters ‘a’ and ‘b’ are found out by theG-R relationship, and peak ground accelerations are calculated for differentperiods e.g., 225yrs, 475yrs, and 2475yrs for 20%, 10%, And 2% exceedance of probabilities, respectively.