Numerical Modelling of Basin Effects on Earthquake Ground Motions in Kutch Basin

Abstract

AbstractThe Kutch Basin in Western India has experienced one of the deadliest earthquakes on 26 January 2001 with 20,000 fatalities and an economic loss of around 5 billion USD. Though the strong motion records of the Kutch region indicate the effects of basin on the ground motion, there are no detailed numerical studies concerning the basin effects. Therefore, a sincere attempt is made to study the basin effects in Kutch region. Initially, a three-dimensional linear seismic site response analysis is carried out for the simplified Kutch Basin of size (150 × 90 × 1.5) km subjected to ricker wave, using the spectral element code SPEED. The average shear wave velocity profile of the Kutch region reported in the literature is adopted in the study. It is found out from the 3D numerical analysis that the maximum amplification occurs at the corner of the basin where the interference of waves reflected from multiple edges happen. Then, a two-dimensional non-linear seismic site response analysis is carried out for the numerical Kutch Basin model using a finite difference programme FLAC. The 2D numerical Kutch model has the similar shape and depth to width ratio as the actual Kutch Basin and is subjected to the recorded earthquake motion at SIVLAKA station (SIV) in Kutch region. The amplification pattern obtained from the 2D numerical model compares well with that of field studies. Further, based on the developed 2D model, parametric studies are carried out and basin amplification factors are computed for various locations of the basin.KeywordsBasin effectsKutch BasinSPEEDFLACSeismic site response