Modelling the 2D seismic response of the Kutch basin on the Indian Subcontinent

Abstract

The Kutch region in India experienced one of the largest intraplate earthquakes on January 26, 2001, with approximately 20,000 fatalities. Although strong motion recordings from the aftershocks in this region indicate basin effects, no detailed numerical studies on the effect of the basin on the ground surface motion in this region have been reported. In the present study, we conduct a 2D non-linear seismic site response analysis of a shallow triangular basin model with various bedrock slopes using the finite difference method to examine the behaviour observed in the Kutch basin. The spatial amplification pattern of the ground motion in the basin with a bedrock slope 10⁰ accords with the recorded ground motion data. The developed basin model is tested with different earthquake motions recorded at various basins across the world. We then develop the amplification factors with respect to the rock outcrop for the peak ground motion parameters and Arias Intensity. Significant amplification is observed at the basin centre and the region between the centre and the edge. The frequency content of the surface motion shifts from a narrow to a broad spectrum from the edge towards the basin centre.