Effects of strong lateral discontinuity on ground motion characteristics and aggravation factor

Abstract

This paper presents the effects of strong lateral discontinuity (SLD) in basins on the ground motion characteristics, differential ground motion (DGM) and aggravation factor (aggravation factor is simply the extra spectral amplification due to complex 2D site effects over the 1D response of the soil column). The seismic responses of open- and closed-basin models with SLD were simulated using SH-wave finite difference algorithm with fourth-order spatial accuracy. Simulated seismic responses, DGM and its spectra revealed that SLD induces Love waves, and the lower cutoff frequency for the same is equal to the fundamental frequency (f0) of the soil layer. The maximum average aggravation factor (AAF) and DGM were obtained near the edge of open basin and at the centre of closed basin. A decrease of amplitude of Love wave, DGM level and AAF with offset from SLD was observed in an open basin. On the other hand, in closed basin, spatial variation of AAF and DGM level was highly variable. Duration of shaking, AAF and DGM level was more in the closed basin than in an open basin. Increase of DGM level and AAF with decrease of the width of basin was observed.