Ring of Fire subduction of the Pacific Plate and the Philippine Sea Plate. As many as 1,500 earthquakes are recorded yearly, and magnitudes of 4 to 6 are not uncommon. Minor tremors occur almost daily in one part of the country or another, causing some slight shaking of buildings. Major earthquakes occur infrequently; the most famous in the 20th century were: the Great Kantō earthquake of 1923, in which 130,000 people died; and the Great Hanshin earthquake of 17 January 1995, in which 6,434 people died. On March 11, 2011 a magnitude 9.0 earthquake hit Japan, the country's biggest ever and the fifth
Imperial Japanese Navy Air Service and the first one to be completed as from the keel up. In the 1920s, the larger percentage of aircraft that were initially acquired and inducted into service, were land based seaplanes whose main tasks were reconnaissance and anti-submarine patrols. The Japanese had drawn up plans for the formation of 17 squadrons of these aircraft, but budgetary constraints limited the units to eleven until 1931. Under the terms of the Washington Naval Treaty two incomplete capital ships were allowed to be rebuilt as carriers, for the Japanese; and . However, "Amagi" was damaged during the Great Kanto earthquake in 1923