Magnitude and Return Period of the Maximum Plausible Earthquake in the Himalaya

Abstract:

We estimate the magnitude and return period of the largest plausible earthquake that could occur on the Main Himalayan Thrust (MHT). Our approach is probabilistic but takes into account the physical constraints that seismic and aseismic slip must add to match the long-term slip rate on the fault. We thus use the rate of moment deficit buildup derived from the pattern of locking of the fault derived from modeling geodetic measurement of interseismic strain to place an upper bound on the average seismic rate release. We also make use of the instrumental and historical seismicity and the related Gutenberg-Richter (GR) statistics. Our method also takes into account aftershocks of the earthquakes with magnitudes larger than those in the instrumental catalog began, as the may substantially contribute to the slip budget. The method yields an estimate of the probability distribution of the magnitude and return period of the maximum possible earthquake.