About 10% of the world's active volcanoes are found in Japan, which lies in a zone of extreme crustal instability. They are formed by 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 January 17, 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 largest on record, according to US Geological Survey data. Undersea earthquakes also expose the Japanese coastline to danger from tsunamis.