Numerical simulation of topographical and geological site effects. Applications to canonical topographies and Rognes hill, South East France

A two-year seismological experiment in Rognes (South Eastern France) confirms the site effects responsible for the severe damage experienced during the 1909 Provence earthquake. Many experimental and numerical studies have been dedicated to quantify and understand the effect of topography on seismic ground motion. However, these local amplifications depend on many parameters and their causes are not yet fully known. Numerical simulation is an interesting tool to try to explain these phenomena and simplified models are helpful for parametric analysis. For this, we use a discontinuous Galerkin finite element method to study the amplification along 2D profiles. First, an extensive numerical study considering an idealized hill topography investigates the combined effects of the steepness, heterogeneity and the angle of incidence on the surface response and focuses in particular on strong amplifications recorded in gentle slope configurations. Secondly, simulations are applied to a realistic 2D profile of the Rognes area. The confrontation of these numerical results with data from a seismological survey help to confirm the influence of both the topography and in-depth geology.