Stochastic Finite Faulted Ground-Motion Simulation Incorporating Slip Effect and Time Duration

Abstract

The 26 ^th January 2001 Bhuj earthquake (Mw 7.6) was one of the most destructive intraplate seismic events in India having peak ground acceleration (PGA) upto 0.37g [1]. An inhouse stochastic finite-fault code built on the dynamic-corner-frequency formulation, incorporating heterogeneous fault slip and variable-density site-amplification model for the soft Ahmedabad alluvium and validated with station records. The high-frequency decay parameter kappa (κ 0.0237) is obtained from the record and validated by Mw 5.3 aftershock recorded at a second station. At the true station distance the simulation reproduces the observed PGA to within 1% and the Fourier and 5%-damped response spectra without systematic bias. The model successfully captures the deep-basin resonance near 0.55 Hz. Unlike the stable Kachchh region, which exhibits high stress drops, the Himalayan collision zone is characterized by active tectonic convergence, complex crustal geometries, and higher near-surface energy attenuation. Hence, because of the active tectonic and unique crustal rheology characteristics of the Himalayan zone, it is essential to recalibrate regional stress drops, path-duration functions, and energy loss parameters in order to accurately simulate such events. Furthermore, in the paper, developed modeling approach is also applied for simulating the 1999 Chamoli Himalayan event (Mw 6.8).