The upper boundary of the Philippine sea plate beneath the western Kanto region estimated from S-P-converted wave

In the Kanto-Tokai district of central Japan, the configuration of the subducting Philippine Sea plate has been estimated using three-dimensional velocity inversions of the seismic wave velocity structure and the distribution of microearthquakes. However, it is difficult to show the configuration of the Philippine Sea plate from the distribution of microearthquakes beneath the western Kanto region, i.e. the Yamanashi and Nagano prefectures, because seismic activity is quite low there.