WESTWARD MIGRATION OF THE IZU-BONIN TRENCH, NORTHWARD MOTION OF THE PHILIPPINE SEA PLATE, AND THEIR RELATIONSHIPS TO THE CENOZOIC TECTONICS OF JAPANESE ISLAND ARCS

The essential elements in the understanding of the Cenozoic island arc tectonics of the Japanese Islands came from reconstructing the paleo-position of the plate boundaries and estimating the change in the Philippine Sea Plate motion. By using the 2nd law of the convergence rate of plates, it was estimated that the Izu-Bonin Trench wandered around 400 km east from its present position during the Paleogene and migrated westward thereafter. Island-arc tectonism is related to the convergence rate of plates (1st law of the convergence rate of plates), hence the changes in the Philippine Sea Plate motion was examined by compiling paleomagnetic data. As a result, the main events of the Cenozoic tectonics of Japan were well explained by the change in the position of the plate boundaries and the change in motion of the Philippine Sea Plate. © 1990.