A numerical study on the basin edge effect on soil amplification

In this paper a numerical study on the effects of the basin edge on the dynamic behavior of the model basins are investigated. For this purpose a range of bedrock inclinations at the valley sides from slighter 10° and 20° to steeper 30° and 40° are selected. A numerical study using nonlinear code which utilizes appropriate static and dynamic boundary conditions, and includes hysteresis damping formulation based on user defined degradation curves is conducted utilizing two sandy and clayey materials. Using several different real earthquake motions provide opportunity for the assessment of the site response to the variation of the motion intensity. The analyses results are presented in the form of the acceleration and spectral acceleration amplification curves. Also, by conducting 1D analyses along the valley the aggravation curve for every case are evaluated and discussed. It was seen that variation of the bedrock inclination not only affects the peaks of the spectral amplification curves, but also the position of the maximums of the curves on the valley surface are changed. Also, the frequency domain results show that different parts of the valleys are sensitive to different periods. While the lateral parts are sensitive to lower periods, the maximum amplification of the inner parts takes place at higher periods. Based on results the 2D behavior not only is dominant at the latreal parts of the valley, but also affects the behavior of the inner parts. Also, the use of the 1D analyes for the estimation of the 2D behavior remains insufficient. Finally, the results of this research show the important effect of the motion intensity on the 2D behavior of the valley specially on the increase of the resonance period at higher period.