Seismic Wave Scatter Study in Valleys Using Coupled 2D Finite Element Approach and Absorbing Boundaries

Abstract

Topographical and mechanical properties of soil layers can lead to amplification or attenuation of seismic waves. Such a phenomena can be theoretically explained by means of ground response analysis. Definition of boundaries is of great concern in modeling ground response and application of boundaries with any constrain can lead to so called “trap box” effect in seismic waves in the model and hence to fictitious results. In present study, two-dimensional Finite Element Method (FEM) is applied in which boundaries known as “absorbing boundaries” are used to study the effect of wave scatter in valleys with different forms on the amplification or attenuation of SV waves. Comparison of the results is conducted for the current approach and those of the coupling Finite Element and the Infinite Element (sometimes called as FE-IFE) method. The results are also presented in non-dimensional diagrams of Au and Av for horizontal and vertical displacement amplitude respectively, through the valley span and its surrounding area. Comparison of the results also indicated that the proposed boundaries can improve the seismic analysis when coupled with the FEM. Also because of topographic irregularities, variations of displacement are seen inside the valley and around it.