No abstract

KEYWORDSGround response; Finite element; Absorbing boundary; Topographic irregularity.Abstract. Topographical and mechanical properties of soil layers can lead to ampli cation or attenuation of seismic waves. Such a phenomenon can be theoretically explained by means of ground response analysis. De nition of boundaries is of great concern in modeling ground response, and application of boundaries with any constrain can lead to the socalled \trap box" e ect on seismic waves in the model, and hence to ctitious results. In the present study, two-dimensional Finite Element Method (FEM) is applied in which boundaries, known as \absorbing boundaries", are used to study the e ect of wave scatter on valleys with di erent forms of the ampli cation or attenuation of SV waves. Comparison of the results is conducted for the current approach and those of the coupling Finite Element and the In nite Element (sometimes called as FE-IFE) method. The results are also presented in non-dimensional diagrams of A u and A v for horizontal and vertical displacement amplitudes, respectively, through the valley span and its surrounding area. Comparison of the results indicate 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.

Abstract. In the occurrence of an earthquake, local site conditions such as soil characteristics, dimension of topographic irregularities, seismic bedrock depth, etc. as well as characteristics of incident wave have important e ects on seismic ground response. In this study, Finite Element Method (FEM) coupled with viscous boundaries is used to evaluate the e ect of empty two-dimensional valleys on ampli cation or attenuation of seismic waves. Parametric studies are carried out and the e ects of dimension of the topography, frequency of the incident wave, and bedrock depth on the seismic ground response are considered using non-linear method in a time domain analysis. Results are shown by means of horizontal and vertical ampli cation ratios in valley span and its surrounding area. It is concluded that displacement variation on ground surface due to topographical e ects is a considerable factor to select a site location or design structures in the valley mount and its surrounding area.

No abstract

No abstract