EFFECTS OF BASIN GEOMETRY MODEL ON SEISMIC SITE RESPONSE ANALYSIS

Abstract

Ground response analysis of seismic waves can utilize a one-dimensional model that represents the soil layers as unbounded layers. This model is suitable for locations within large soil basins where there are no significant changes in the basin geometry. However, for small basins, the propagation and reflection of seismic waves within the basin may significantly affect the response of the ground. This article presents a study on the effects of the basin geometry, including the width of the basin and the slope of its edges, on the ground response to seismic waves using a two-dimensional model. The study considers the response at various locations by equivalent linear analysis of the finite element model. The process begins by presenting the steps for adjusting the parameters of the two-dimensional model to match the results of the one-dimensional model, which provides consistent results for large basins. Then, the acceleration response spectra obtained from both methods are compared. The results show that for large basins with a width-to-depth ratio of approximately 20, the analysis using the one-dimensional model produces results that are close to those obtained from the two-dimensional model. However, for smaller basins, such as those with a width-to-depth ratio of approximately 5, the results from the two-dimensional model may be significantly higher than those from the one-dimensional model, by up to approximately 70%. Additionally, the results indicate the importance of the slope of the basin edges in influencing the shape of the basin. For instance, if the edges have a slope of 45 degrees, the results from the two-dimensional model may be significantly higher than those from the one-dimensional model, by up to approximately 90%.