New criteria on the filling ratio and impedance ratio effects in seismic response evaluation of the partial filled alluvial valleys

An extensive numerical analysis on the seismic site effects due to local topographical and geotechnical characteristics is carried out. 2D configurations under incidence of vertically propagating SV waves is modeled with the aid of HYBRID program, combining finite elements in the near field and boundary elements in the far field. The filling ratio and the impedance ratio effects on the modification of the seismic response of alluvial valleys are underlined. Parametric analysis is done on the central point of alluvial valleys where the critical point of response under existence of sediments stands. Specifying the amplification pattern under filling ratio effects, effective geometrical parameters are introduced. Subsequently, to assess the effect of the type of sediments on the seismic response, mechanical properties of materials are changed and impedance contrast coefficient is considered in combination with geometrical parameters. Finally, practical curves are presented for engineering applications.

► Seismic site effects are studied with the aid of a hybrid (FE/BE) numerical method. ► Filling ratio and the impedance ratio effects of alluvial valleys are focused. ► Amplification pattern of valleys based on shape and filling ratio are displayed. ► Impedance ratio effect is considered in combination with the geometrical parameters. ► Practical curves including complex site effects are presented for engineering uses.