Determination of Response Spectra for Sri Lankan Cities using Finite Difference Method

Sri Lanka has been considered as a seismically safe country in the past considering the large distance from the island to active plate boundaries. However, with the increased degree of urbanization, the possible impact of intraplate earthquakes on population centres within the island has become important. In this context, deterministic and probabilistic seismic hazard assessments have been carried out by few researchers so far. However, these studies have not considered the influence of variation of bedrock profile on the seismic wave propagation. In the study presented here, a numerical simulation is carried out to investigate the effect of variation of the bedrock profile on the seismic wave propagation in Sri Lanka. The acceleration time histories of seven real time earthquake records, selected from the PEER database, were used as input in a numerical finite difference model simulating the two-dimensional bedrock response. The resultant spectra at the bedrock surface thus obtained are compared with those derived from the early studies. The comparison clearly shows the effect of ground elevation profile on seismic wave propagation, which should be taken into account especially when designing earthquake resistant structures in higher elevation areas.