After the opening of the Sea of Japan, the country became an island arc isolated from the Asian continent. The main parts of the Japanese Islands are called the Honshu Arc, including not only Honshu, but also Kyushu, Shikoku and Hokkaido islands. The basement of the arc is composed of Paleozoic to Cenozoic rocks accreted by ocean plate subduction along the Asian continental margin. The Honshu Arc is divided into the Southwest Honshu (or Japan) Arc and the Northeast Honshu (or Japan) Arc by the Fossa Magna in central Japan. The Pacific Plate is being subducting along the Japan Trench beneath the northeastern part of the Honshu Arc. Subduction of the cold and old oceanic plate caused tectonic erosion along the Japan Trench. Huge amounts of rock previously accreted were removed by tectonic erosion (Suzuki et al., 2010; Yanai et al., 2010). On the other hand, the young Philippine Sea Plate is being subducted and forming an accretionary wedge along the Nankai Trough in Southwestern Japan. The collision between the Honshu and Izu arcs provided trench-fill sediments for the accretionary wedges and compression which uplifted the accretionary wedges to form the Boso Peninsula. Extensive volcanic activity has occurred due to plate subduction beneath the northeastern Honshu Arc. The strong, 9.0 magnitude, earthquake in northeast Japan in March 11, 2011 was triggered by subduction of the Pacific Plate beneath the Honshu Arc along the Japan Trench. Reverse fault movement between the Honshu Arc and the Pacific Plate was the main cause of the massive tsunamis. In the southwestern part of the Honshu Arc, volcanic activity is not as active, as in the north east, except in the Kyushu region, where extension tectonics causes rifting and active volcanism. Sometimes earthquakes occur along the Nankai Trough as the result of plate subduction.