The seismic activity that inclines downward from the upper right in the middle of the figure (south) to the lower left, occurs along the subducting Philippine Sea Plate. From the distribution of these earthquakes, it is apparent that the Philippine Sea Plate is subducting under the Kanto region. Also, seismic activity deeper than 100 km in the figure is within the Pacific Plate.

[Compiled from data from the National Research Institute for Earth Science and Disaster Prevention]