Effects of fold structure in the kashiwazaki-kariwa nuclear power station on the ground motion characteristics of Niigataken Chuetsu-Oki Earthquake: Modeling of sub-surface structure and wave propagation study using a finite difference method

In the Kashiwazaki-Kariwa Nuclear Power Station, the seismic ground motion in the south side of the site, was significantly larger than that in the north side of the site, in the 2007 Niigataken Chuetsu-oki earthquake. In order to analyze the effects of geological structure below the site on the seismic ground motion characteristics in the site, we made 2-D soil model and simulated the seismic ground motion with the model using the finite difference method. The soil model was estimated by the result of the geological investigations and described the folding structure just below the Kashiwazaki-Kariwa Nuclear Power Station. For input motion, we defined point source or plane wave, and we considered many directions as the incidence angle. From the result of analysis, we concluded that seismic wave concentrated in the local area of the site with the influence of the complex ground structure, and the ground motion in the south side became larger than that in the north side..