Abstract
In order for a municipality to formulate disaster management plan on earthquake, damage estimation has to be carried out as the first stage. In the case that a city is formed on soft soil deposits like Kofu city, it is important to evaluate earthquake ground motion and ground strain in consideration of local site effect. Though it is known that local site effect of earthquake motions in alluvial soil deposits irregularly bounded by bedrock brings about local concentration of damage, the damage estimation by three-dimensional numerical analysis have not be conducted due to the restriction of computational resource. However, together with the development of computational science technology, large-scale analysis on three-dimensional nonlinear seismic ground response has become executable at the present time. Thus, local site effects, especially for local concentration of strain in surface soft soil deposits are examined in this paper. Seismic responses of an ideal alluvial soil model and the surface soil model for a part of Kofu basin are evaluated using three-dimensional nonlinear FEM analyses. The results of analyses imply the significance of three-dimensional nonlinear analyses of surface soil deposits in earthquake damage estimation.
