MODELISATION OF TOPOGRAPHIC SITE EFFECT 3D AT THE LOW NOISE UNDERGROUND LABORATORY (LSBB), RUSTREL, FRANCE

摘要

The local geology related to topographic site effects is known to have a strong impact on the amplifications and attenuations of the ground motion. The SHAKE3D finite difference code [Cruz-Atienza et al., 2007] allows studying the influence of various local structures and rheological parameters on the seismic response at the surface. The ground motion is simulated in a realistic heterogeneous 3D model. This model integrates the mountainous topography above the Low Noise Underground Laboratory, Rustrel, France (http://lsbb.unice.fr)and the medium properties deduced from seismic imaging experiment done in 2006.Such a topography is typical in the South-East region of France : steep slope (greater than 30%) and sharp crest followed by a broad plateau. This configuration also allows investigation of coupled basin-topographic responses at the regional scale.We consider several models taking into account the spatial variation of the rheological parameters VP, VS, QP,QS, and density together with the topography. Sources with different locations and radiation patterns are also considered relatively to the geometry of the topography. These simulations help us to improve our knowledge of the topographic effects taking into account the heterogeneity of medium and the complexity of the topography.