DYNAMIC RESPONSE OF STRUCTURES DUE TO BASIN GENERATED RAYLEIGH WAVES

Abstract

Basin is a depressed area in underlying rock filled with sediments. The basin affects all the three ground motion characteristics namely amplitude, duration and frequency, therefore, they become crucial consideration in seismology. Due to the complex interaction of body-waves with the geological structure of the sedimentary basin leads to generation of basin-induced surface waves. The analysis of the basin-generated surface (BGS) waves and the associated variations in ground motion is very important since the flat layer response sometimes becomes inadequate in explaining the observed damages as are reported in some past major earthquakes near the basins. In the present study we have tried to quantify the response of building situated in a shallow elliptical basin due to basin-generated Rayleigh waves using the Finite difference method. For the simulation of the SV-waves, fourth order staggered grid wave FD program given by Narayan and Kumar, 2014 is used for getting recording the response in the rock, homogenous soil and basin models. The validation of the numerical model has been carried out and the results have been compared with the analytical results. After this, we have studied the basin-effects by implementing four standalone buildings of different heights at different locations in shallow-elliptical basin and compared their responses with same buildings in equivalent homogenous sediment deposit. Three major effects i.e., the amplitude amplification, a significantly longer duration of the ground motion and a more rapid spatial variation of the peak ground motion were observed due to the basin-effects.