Integrated Earthquake Simulation of Earthquake Hazard and Disaster

An earthquake is failure of the Earth's crust. As an example, we take a look at the Japanese Islands, which are located near boundaries of the four plates; namely, the Pacific Ocean Plate, the Philippine Sea Plate, the Eurasia Plate and the North America Plate. These plates are moving at the speed of a few centimetres per year in different directions, and mismatch in their displacement generates stress in the plate boundary or inside of the plates. Earthquakes are caused as the failure of some part of the plate boundaries or of the plate itself when the accumulated stress reaches a critical value

On the vertical cross section, we observe that the Pacific Ocean Plate subducts itself under the Eurasia Plate. The Pacific Plate is bent like a beam, and stress state is tensile or compressive in the upper or lower part of the plate slab, respectively. Earthquakes take place in these places. More important is shearing stress that acts on the boundary between these two plates. This shearing stress is the cause of earthquakes of largest size when a large area of the plate boundary is broken. An earthquake of this kind is called an interplate earthquake. An earthquake that takes place in the plate is called an intraplate earthquake