The Commission on the Limits of the Continental Shelf (CLCS) established pursuant to the United Nations Convention on the Law of the Sea issued its recommendations on Japan's extended continental shelf in April 2012, confirming Japan's rights over the vast areas within the Philippine Sea and Pacific Plates. Japan submitted information on the limits of its continental shelf beyond the EEZ to the CLCS in November 2008, which was the result of a 25-year continental shelf survey project begun in1983, involving all of Japan's agencies related to geosciences (Hydrographic and Oceanographic Department of Japan Coast Guard, Japan Agency for Marine-Earth Science and Technology, Japan Oil, Gas and Metals National Corporation, and Geological Survey of Japan) . The huge volume of geological and geophysical data obtained by the project gives the scientists an unprecedented opportunity to study the geology and tectonics of the Philippine Sea and Pacific Plates. In this contribution, we review the results of these studies, summarizing the following seven main themes: (1) Extensive and high-density mapping of the Philippine Sea, establishing a precise evolutionary history of the plate; (2) Discovery of oceanic core complexes within the Philippine Sea Plate; (3) Dense bottom sampling of the Philippine Sea Plate, establishing a precise tectono-magmatic history of the plate; (4) Understanding the crustal structure of ridges and basins within the Philippine Sea Plate; (5) Understanding the collision tectonics of the Ogasawara Plateau; (6) Understanding the crustal structure of seamounts and basins within the Pacific Plate; (7) Discovery of hydrothermal field within the Okinawa Trough and Izu-Ogasawara Arc.
