SEISMIC RESPONSE OF SHALLOW ALLUVIAL VALLEYS - THE USE OF SIMPLIFIED MODELS

A method is proposed to approximately compute the seismic response of shallow three-dimensional (3D) alluvial valleys. It is based on the ex act solution for a simple configuration. Namely, the antiplane respons e of a rectangular deposit with a moving rigid base. In such a solutio n, which is used as a framework for our approximations, the spectral s ignature of locally generated surface waves is explicit. Thus, an appr oximate expression is constructed to separately account for one-dimens ional (1D) response and lateral effects. Results are presented for two - and three-dimensional cases. Comparisons are provided with rigorous solutions as well. Our formulas allow for fast computations.