Influence of soil properties and geometrical characteristics of sediment-filled valleys on earthquake response spectra.

Abstract : It is well-known that the response of a site to seismic excitation depends on both its local topography and its soil properties. Although the recent building codes (i.e. Eurocode8) incorporate these site effects, they only take into account unidimensional ones and ignore complex cases due to two-dimensional irregular configurations. Recent work has been mainly focusing either on the development of numerical methods allowing always more precise results or on the elaboration of simplified approaches usable for engineering purposes. The aim of this work is to propose a simple criterion, combining soil properties and geometrical characteristics of valleys to estimate the amplification of earthquake response spectra in sediment-filled valleys. We will first study the response of unidimensional soil layers to obtain a criterion that can be extended to bidimensional configurations. The seismic input is a synthetic SV Ricker wave with vertical incidence. Horizontal displacements at surface points are computed by using the HYBRID code which combines finite elements in the near field and boundary elements in the far field (FEM/BEM).