Seismic Response of 2D Triangular-Shaped Alluvial Valleys to Vertically Propagating Incident SV Waves

This paper presents the results of a numerical parametric study on the seismic behavior of 2D triangular-shaped valleys subjected to vertically propagating incident SV waves. The medium is assumed to have a linear elastic constitutive behavior. All calculations are executed in time-domain utilizing the spectral finite element method. Clear perspectives of the amplification patterns of the valley are presented by investigation of the frequency-domain responses. It is shown that the amplification pattern of the valley and its frequency characteristics depend strongly on its shape ratio. The maximum amplification ratio along the ground surface occurs at the centre of the valley. A simple formula has been proposed for making initial estimation of the natural period of the valley in site effect microzonation studies. The natural frequency of the alluvial valley decreases as the shape ratio of the valley decreases; moreover, the value of the natural frequency of the triangular alluvial valley is bigger than the natural frequency of the corresponding rectangular alluvial valley.