Regional extent of the S wave reflector beneath the Kanto District, Japan

An S wave reflector was found near the upper plane of the double seismic zone associated with the subducting Pacific plate beneath the southern Kanto district of Japan. Here the areal extent of the reflector is confirmed for a region ranging from 34.5°N to 36.7°N, from the analysis of the travel times of the reflected S waves on 8‐Hz band seismograms. A bend of the reflector is found at about 36°N. It is coincident with the bend of the upper boundary of the subducting Pacific plate obtained from the seismicity analysis. In the middle of the Kanto district the reflector extends to a depth of 120 km, whereas in the northern Kanto district it extends just beneath the volcanic front. The reflector could not be verified for depths shallower than 60 km depth because the reflected S wave cannot be identified at the eastern most stations of the network.