In the framework of the reevaluation of the seismic hazard for the Tricastin NPP, a specific study is conducted to evaluate the site effect related to the thick sedimentary layers and the multi-dimensionality of the Rhone Valley. In particular, the adjustment factors to be applied to regulatory spectra to account for such site effects are evaluated based on 1D and 2D modeling using finite difference algorithm with constraints from empirical data.