Three Dimensional P and S Velocity Structures of Uppermost Mantle beneath Kanto, Tokai and Chubu Districts, Japan

Abstract

We obtained three-dimensional P and S velocity structures of the uppermost mantle beneath the Kanto, Tokai and Chubu districts, Japan, by means of travel time tomography. We used 18 years travel time data recorded by the National Research Institute for Earth Science and Disaster Prevention. High velocity subducted Philippine Sea plate is revealed below the Kanto and Tokai district. Low velocity oceanic crust of the Philippine Sea plate is also revealed below the Kanto and Tokai district. The oceanic crust below the Kanto area is found to be a complex shape, which shows the deformation of the Philippine Sea plate. High velocity area, ahead of the leading edge of the Philippine Sea plate associated with seismic activity, suggests the existence of the aseismic plate. Some high Poisson's ratio areas are found in the low velocity areas.