Recent and Present-Day Subduction and Collision Along the Northern Tip of the Philippine Sea Plate

Abstract

The northernmost converging boundary of the Philippine Sea (PHS) plate crosses the base of the Izu Peninsula about 60 km southwest of Tokyo, subducting beneath Japan, a part of the Eurasian (EUR) plate. The 1923 Kanto earthquake ( M s = 8.2) occurred along the portion east of the peninsula and another underthrust event ( M ˜ 8) is expected in the foreseeable future along the portion west of the peninsula. Consequently, a vast amount of data has been and is being accumulated in various fields, including geodesy, seismology, submarine geology and geophysics. This paper tries to give a unified interpretation of the above observations across and along the 200 km long plate boundary in terms of a plate tectonic model in which the PHS plate is subducting beneath and partially colliding with the EUR plate at an annual rate of 3 ˜ 5 cm in a 310° ± 5° direction. Because of the resolving power being greater than usual both in time and space, discrimination between material and mechanical boundaries is necessary for the converging plate boundary.