Three scenario earthquakes, such as Nankai trough mega earthquake, the 1923 Kanto earthquake, and North Tokyo bay earthquake, are selected at Tokyo bay area, based on the seismic hazard analysis and so on. Earthquake ground motions at engineering bed rock are evaluated by the Hybrid synthesis of ground motions derived from the stochastic Green’s function method and the 3D-finite difference method. In addition to the conventional moderate and severe earthquakes (Level 1 and 2), extreme earthquake (Level 3) is newly defined, and their seismic design criterion are proposed.
