The Japanese islands are situated on the eastern board of the Eurasian plate, where it meets the Pacific plate and the Philippine Sea plate. The former is sinking from the east under Japan by several centimeters per year, the latter from the south at the same speed. This exerts constant pressure on the Japan islands, both on the link and inland, and it is this which generates the earthquakes when the pressure is released.
1 Eurasian Plate
2 North American Plate
3 NankaiTrough
4 Philippine Sea Plate
5 Suruga Trough
6 Japan Trench
7 Pacific Ocean Plate
(→indicates the direction of movement of the plates)
Figure 3: Model of the plates around Japan
(iv)The active-fault earthquakes
This kind of earthquake occurs in the plate, and is generated by the dislocation of strata within the plate. Though the level of magnitude is smaller than that of the marine earthquake (from 6 to 7.5), these earthquakes can cause greater disaster because of the nearness of the source of the earthquake.
