EFFECTS OF STRONG LATERAL DISCONTINUITY ON GROUND MOTION CHARACTERISTICS AND AGGRAVATION FACTOR

Abstract

In this dissertation,. we have studied the effects of strong lateral discontinuity (SLD) considering both the open and closed basins on the ground motion characteristics and aggravation factor.. We.have also studied the effects of angle of incidence on the SLD-induced Love waves. Seismic responses of various models were simulated using . software based on staggered grid finite difference approximation of 2D elastodynamic SH-wave equation with fourth order spatial accuracy. Simulated results revealed generation of surface waves near the lateral discontinuity. Spectral analysis, of the differential ground motion depicts that the lower cutoff frequency for Love wave generation. near the discontinuity is the fundamental frequency of the soil deposit. Further, SLD-induced Love waves generate large differential ground motion near the lateral discontinuity. The obtained maximum aggravation factor in case of a' open basin is near the lateral discontinuity it decreases as we go away-from the discontinuity. The obtained 1.5 to 1.6 average aggravation factor amplification reveals that the amplification of seismic waves near the SLD will be 1.5-1.6 times to that obtained by using 1D response of the soil column near the lateral discontinuity. In case of closed basin, it was observed that as the width of the basin decreases, the amplitude of induced Love wave increases near, the lateral discontinuity and, the centre of the basin, same is also revealed in case of aggravation factor. In case of closed basin, the . obtained aggravation factor is more than that of open. basin. The. analysis of simulated results for different angle of incidence reveals that the amplitude of the SLD-induced Love waves and aggravation factor increases with the angle of incidence. In IS codes-emphasis is given on the PGA and PGV. and no provision and discussion is. given for the differential ground motion The findings of this . study reveals that differential ground motion caused by SLD- induced Love waves needs. special . attention during the seismic microzonation or seismic hazard, prediction for the codal designed buildings since it may. play an important role in damage distribution during earthquakes.