The famous earthquakes and volcanoes of Japan are all related to subduction. Japan forms a small part of the "Ring of Fire", the name given for the various subduction zones that surround and consume the Pacific plate on most sides. The Pacific plate subducts westward beneath the Ohkotsk plate along the trench that lies east of the northern island Hokkaido and the main island Honshu. To the north that subduction zone is continuous with the subduction zone beneath the Kurile islands, and to the south with the subduction zone beneath the Izu, Volcano, and Marianas islands. In the latter case, however, the Pacific plate subducts beneath the Philippine Sea plate. That plate, in turn, subducts westward beneath the Eurasian plate to feed the volcanoes of Japan's southern island of Kyushu, and the Ryukyu islands to its south. Notice that the earthquake colors, which are keyed to depth, allow you to image these west-dipping subduction zones.
