Relationship Between Crustal Structure and Plate Convergence Around the Izu Collision Zone in Central Japan

We conducted a receiver function (RF) analysis to understand the convergence process in and around the Izu collision zone. We calculated the P- and S-wave RFs and converted them to depth using a three-dimensional (3D) regional tomography model and regionally estimated near-surface structure. We detected the Moho of the Philippine Sea Plate and determined its 3D geometry in and around the collision zone. In addition, we considered the 3D seismic velocity model, which was previously determined using seismic tomography, and we complemented a part of the Moho that we did not detect using the RFs. Based on the geometry of the upper surface of the Philippine Sea Plate determined in previous studies, the crust is >35 km thick beneath the Izu Peninsula and collision zone and becomes thinner (<20 km) moving east of the collision zone. Thus, the thick crust along the Izu-Bonin arc collides, and the thin forearc crust subducts. A stable slip surface was previously assumed to exist at a 15-20 km depth beneath the Izu Peninsula and the collision zone. This study indicates that the surface should exist within the crust of the Philippine Sea Plate.