Simulation of strong ground motion for a MW 8.5 hypothetical earthquake in central seismic gap region, Himalaya

In this study, hybrid simulation technique is used to simulate acceleration time histories for a hypothetical great earthquake of magnitude Mw 8.5 in central seismic gap (CSG) region of Himalaya. In this technique the low frequency ground motions simulated by Spectral Finite Element Method (SPECFEM) are combined with high frequency ground motions obtained by Empirical Green’s Function (EGF) technique. First, this method is validated effectively by simulating acceleration time histories over all frequency range for the 2015 Mw 7.86 Nepal earthquake. Since 2005, a total of 21 small events whose magnitudes vary from 3.5 to 5.7 have occurred in CSG region. The recorded data of these events are used as Green’s function in EGF technique. Slip distribution over fault plane is considered as a random field for simulating the ground motions. Ensembles of acceleration time histories are simulated at 32 stations in the epicentral region. The maximum horizontal PGA of 0.89g is observed at station Garsain. The mean PGA value exceeded 0.8g at five stations. The estimated acceleration time histories can be used to estimate the safety of the existing structures and design values for the construction of important structures.