Japan was struck on Friday by an earthquake with a magnitude of 8.9, the biggest in about 140 years.
Japan is one of the world’s most earthquake-prone countries, with a tremor occurring at least every five minutes.
Located in the “Ring of Fire” arc of volcanoes and oceanic trenches partly encircling the Pacific Basin, the country accounts for about 20 percent of the world’s earthquakes of magnitude 6.0 or greater. Tokyo, with a population of 12 million, sits on the junction of four tectonic plates: the Eurasian, North American, Philippine and Pacific.
The sudden bending or breaking of any plate can trigger an earthquake.
Following are dates of some major recent quakes.
Aug. 16, 2005 - A major quake with a magnitude of 7.2 rocked a region about 300 km (190 miles) north of Tokyo, injuring more than 80 people. Oct. 23, 2004 - A 6.8 magnitude quake hit the Niigata region, about 250 km (150 miles) north of Tokyo, killing 65 people and injuring 3,000.
Jan. 17, 1995 - A quake of 7.3 magnitude struck, killing more than 6,400 in the western city of Kobe in 1995. It caused $100 billion in damage and was the costliest natural disaster in history.
The Great Kanto earthquake on Sept. 1, 1923, had a magnitude of 7.9. It killed more than 140,000 people in the Tokyo area and seismologists have said another such quake could hit the city any time.