Hybrid stochastic ground motion modeling of the Mw 7.8 Gorkha, Nepal earthquake of 2015 based on InSAR inversion

Abstract

We derive the coseismic slip distribution on a fault for the 2015, Mw 7.8 Gorkha earthquake based on ALOS-2 wide scan data and the inversion code, SDM (Steepest Descend Method). The results show that the maximum slip is 4.7m, and the total released seismic moment is 6.02×1020Nm, equivalent to an earthquake of Mw ∼7.82. Static stress and slip heterogeneity analyses show that both the average stress drop and corner wavenumber are at a low level. Additionally, we model the observed impulsive behavior at the near-source KATNP station using a hybrid stochastic approach, which combines an analytical approach at low frequencies with a stochastic approach at high frequencies. The good agreement between the hybrid modeling and observed records reveals that the input parameters, such as stress drop or slip distribution, are suitable for the Gorkha earthquake. The success of the modeling indicates that, in addition to the smooth onset of STF (slip-rate time function), the low stress drop and low degree of slip heterogeneity are also responsible for the low level of high-frequency ground motion during the Gorkha earthquake.