Simulation of strong ground motion for 1905 Kangra earthquake and a possible megathrust earthquake (Mw 8.5) in western Himalaya (India) using Empirical Green’s Function technique

Abstract

Earthquakes are deadliest among all the natural disasters. The areas that have experienced great/large earthquakes in the past may experience big event in future. In this study, we have simulated Kangra earthquake (1905, Mw 7.8) and a hypothetical great earthquake (Mw 8.5) in the north-west Himalaya using Empirical Green’s Function (EGF) technique. Recordings of Dharamsala earthquake (1986, Mw 5.4) are used as Green function with a heterogeneous source model and an asperity. It has been observed that the towns of Kangra and Dharamsala can expect ground accelerations in excess of 1 g in case of a Mw 8.5 earthquake and could have experienced an acceleration close to 1 g during 1905 Kangra earthquake. The entire study region can expect acceleration in excess of 100 cm/s2 in case of Mw 7.8 and 200 cm/s2 in case of Mw 8.5. The sites located near the rupture initiation point can expect accelerations in excess of 1 g for the magnitudes simulated. For validation, the estimates of the PGA for Mw 7.8 simulation are compared with isoseismal studies carried out in the same region after the Kangra earthquake of 1905 by converting PGA values to intensities. It was found that the results are comparable. The target earthquakes (Mw 7.8 and Mw 8.5) are simulated at depth of 20 km and 30 km to examine the effect of PGA for different depths. The PGA values obtained in the present analysis gave us an idea about the level of accelerations experienced in the area during 1905 Kangra earthquake. Future construction in the area can be regulated, and built environ can be strengthened using PGA values obtained in the present analysis.