The 2011 earthquake off the Pacific coast of TÅhoku, often referred to in Japan as Higashi nihon daishin-sai and also known as the 2011 Tohoku earthquake, the Great East Japan Earthquake, and the 3.11 Earthquake, was a magnitude 9.03 (Mw) undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST (05:46 UTC) on Friday, 11 March 2011, with the epicenter approximately 70 kilometres (43 mi) east of the Oshika Peninsula of TÅhoku and the hypocenter at an underwater depth of approximately 32 km (20 mi). It was the most powerful known earthquake ever to have hit Japan, and one of the five most powerful earthquakes in the world since modern record-keeping began in 1900. The earthquake triggered powerful tsunami waves that reached heights of up to 40.5 metres (133 ft) in Miyako in TÅhoku's Iwate Prefecture, and which, in the Sendai area, travelled up to 10 km (6 mi) inland. The earthquake moved Honshu (the main island of Japan) 2.4 m (8 ft) east and shifted the Earth on its axis by estimates of between 10 cm (4 in) and 25 cm (10 in).
On 12 September 2012, a Japanese National Police Agency report confirmed 15,870 deaths, 6,114 injured, and 2,814 people missing across twenty prefectures, as well as 129,225 buildings totally collapsed, with a further 254,204 buildings 'half collapsed', and another 691,766 buildings partially damaged. The earthquake and tsunami also caused extensive and severe structural damage in north-eastern Japan, including heavy damage to roads and railways as well as fires in many areas, and a dam collapse. Japanese Prime Minister Naoto Kan said, "In the 65 years after the end of World War II, this is the toughest and the most difficult crisis for Japan." Around 4.4 million households in northeastern Japan were left without electricity and 1.5 million without water.
The tsunami caused a number of nuclear accidents, primarily the level 7 meltdowns at three reactors in the Fukushima Daiichi Nuclear Power Plant complex, and the associated evacuation zones affecting hundreds of thousands of residents. Many electrical generators were taken down, and at least three nuclear reactors suffered explosions due to hydrogen gas that had built up within their outer containment buildings after cooling system failure. Residents within a 20 km (12 mi) radius of the Fukushima Daiichi Nuclear Power Plant and a 10 km (6.2 mi) radius of the Fukushima Daini Nuclear Power Plant were evacuated. In addition, the U.S. recommended that its citizens evacuate up to 80 km (50 mi) of the plant.
Early estimates placed insured losses from the earthquake alone at US.5 to .6 billion. The Bank of Japan offered Â¥15 trillion (US3 billion) to the banking system on 14 March in an effort to normalize market conditions. The World Bank's estimated economic cost was US5 billion, making it the most expensive natural disaster in world history.