Fig. 5

Various types and depths of earthquakes in and around Japan. Very shallow earthquakes occur at active faults or near the volcanic active areas. At an active fault in Japan, an M7 earthquake occurs about once in a 1000 years to several thousand years. Shallow thrust-type interplate earthquakes occur at plate boundaries along trenches and troughs off the Pacific side of Japan. An M8 earthquake occurs about once in a 100 years to a few hundred years at one section of those. Near the outer rise of the oceanic plate, normal fault-type intraplate earthquakes occur at the shallow depth. Intermediate depth intraplate earthquakes occur in the subducting slab just beneath the Japan Archipelago. Since the stress drop of the intraplate earthquake is larger than that of the interplate earthquake, stronger short period waves are felt in remote sites