On the Relationship between the Geometry of Subducted Philippine Sea Plate and the Crustal Deformation around Izu Peninsula, Japan

Abstract

We propose a model for the cause of peculiar shape of the slab beneath Tokai region. The characteristics in the shape of the subducted slab of Philippine Sea plate in this region are ; (1) an aseismic region to the northwest of Izu peninsula, (2) overlapping of seismic zones beneath Nobi plane around Nagoya, (3) sharp bent of the trough axis between Nankai and Suruga trough. The shape can be interpreted as an effect of the shear deformation around Izu Peninsula. The deformation is produced by both the collision of Izu Peninsula to Eurasian plate and frequent dike intrusions in the volcanic region from Izu-Oshima to eastern Izu Peninsula. Consequently the moving direction of the slab rotates anti-clockwise and the slab moves over the neighboring slab subducted from Nankai trough. This directional change also produce a we ge-shaped gap to the northwest of Izu Peninsula. The shear deformation is consistent with the focal mechanisms and the result of GPS measurement in this region.