抄録
The southern Kanto district, central Japan, is characterized with its quite complex tectonic environment. Both of the Pacific and the Philippine Sea plates are subducting beneath this area and interfering each other. Adjoining this area, there exists the Izu Peninsula to the west as a collision zone between the Pacific and the Eurasian plates, while there exists trench-trench-trench triple junction of the Pacific, Philippine Sea and the Eurasian plates to the east.
Several models of the plate configuration in this area have been proposed based onthe hypocentral distribution of microearthquakes, the focal mechanism solutions, the three-dimensional velocity structure, the fault model of major earthquakes, the geomorphological and geological evidences, and so on. Comparing these models, considerable varieties are seen in the iso-depth contours of the Philippine Sea plate, whereas those of the Pacific plate are more or less similar. These varieties came from the differences in the data source, the strike of the cross sections which were mainly used for delineation of the contour lines, and referenced data on which each researcher put different stresses.
Based on these tectonic models, some explanations are given to the paired earthquake phenomenon and synchronized seismic activation among the adjacent regions. Also, several candidates for forthcoming earthquakes of M7 class are proposed as a consequence of these tectonic backgrounds.
