ENGINEERING PERSPECTIVE FOR THE SEISMIC SITE RESPONSE OF ALLUVIAL VALLEYS

The seismic site response of alluvial valleys with limited width is ev aluated using three engineering models. The models are based on the on e-dimensional, two-dimensional and the frame model approaches. The obj ective is to analyse the effects of the main parameters governing surf ace motions and provide engineering guidance for predicting them. The limitations on the use of the one-dimensional model in site response e valuation in valleys are pointed out. The frame model, which accounts for the limited width of valley, gives response results that are in go od agreement with the two-dimensional model results. It is found that the effect of the two-dimensional amplification is significant over a distance from the valley edges beyond which the response may be adequa tely represented by one-dimensional analysis. The soil amplification v aries depending on the soil type, site location relative to the valley and the dominant period and amplitude of input rock record. (C) 1997 by John Wiley & Sons, Ltd.