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| date = 11 March 2011 | origintime = 14:46:24 JST (UTC+09:00) | duration = 6 minutes〔 | magnitude = 9.0 Mw〔〔 | depth = | location = | type = Megathrust | countries affected = Japan (shaking, tsunami) Pacific Rim (tsunami) | damage = Tsunami wave, flooding, landslides, fires, building and infrastructure damage, nuclear incidents including radiation releases | intensity = IX (''Violent'') | PGA = 2.99 ''g'' | tsunami = Up to in Miyako, Iwate, Tōhoku | landslide = Yes | foreshocks = List of foreshocks and aftershocks of the 2011 Tōhoku earthquake | aftershocks = 11,450 (as of 3 March 2015)〔(震度1以上の余震の最大震度別地震回数表（3月11日～） ) on 4 March 2015. Japan Meteorological Agency. Retrieved 11 March 2015.〕 | casualties = }} The was a magnitude 9.0 (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 epicentre approximately east of the Oshika Peninsula of Tōhoku and the hypocenter at an underwater depth of approximately .〔 The earthquake is also often referred to in Japan as the 〔(Abstract of the 191th meeting of CCEP ) - website of the Japanese Coordinating Committee for Earthquake Prediction〕 and also known as the 2011 Tohoku earthquake,〔(USGS Updates Magnitude of Japan’s 2011 Tohoku Earthquake to 9.03 ) - website of the United States Geological Survey〕 and the 3.11 earthquake. It was the most powerful earthquake ever recorded to have hit Japan, and the fourth most powerful earthquake in the world since modern record-keeping began in 1900.〔 The earthquake triggered powerful tsunami waves that reached heights of up to in Miyako in Tōhoku's Iwate Prefecture,〔Yomiuri Shimbun evening edition 2-11-04-15 page 15, nearby Aneyoshi fishery port (姉吉漁港)(Google map E39 31 57.8, N 142 3 7.6) 2011-04-15, (大震災の津波、宮古で38.9 m…明治三陸上回る ) by okayasu Akio (岡安 章夫) 〕 and which, in the Sendai area, travelled up to inland. The earthquake moved Honshu (the main island of Japan) east, shifted the Earth on its axis by estimates of between and ,〔〔 and generated sound waves detected by the low-orbiting GOCE satellite. On 10 March 2015, a Japanese National Police Agency report confirmed and across twenty prefectures, as well as 228,863 people living away from their home in either temporary housing or due to permanent relocation. A 10 February 2014 agency report listed 127,290 buildings totally collapsed, with a further 272,788 buildings 'half collapsed', and another 747,989 buildings partially damaged.〔("Damage Situation and Police Countermeasures... February 10, 2014" ) National Police Agency of Japan. Retrieved 17 February 2014.〕 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.〔〔Saira Syed – ("Japan quake: Infrastructure damage will delay recovery" ) – 16 March 2011 – ''BBC News'' – Retrieved 18 March 2011. 〕 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 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 resulting from the loss of electrical power. Residents within a radius of the Fukushima Daiichi Nuclear Power Plant and a radius of the Fukushima Daini Nuclear Power Plant were evacuated. Early estimates placed insured losses from the earthquake alone at US$14.5 to $34.6 billion. The Bank of Japan offered ¥15 trillion (US$183 billion) to the banking system on 14 March in an effort to normalize market conditions. The World Bank's estimated economic cost was US$235 billion, making it the costliest natural disaster in world history. ==Earthquake== The 9.0 magnitude (Mw) undersea megathrust earthquake occurred on 11 March 2011 at 14:46 JST (05:46 UTC) in the north-western Pacific Ocean at a relatively shallow depth of 32 km (19.9 mi),〔〔(Japan earthquake and tsunami: what happened and why|World news ). The Guardian. Retrieved on 2011-04-03. 〕 with its epicenter approximately 72 km (45 mi) east of the Oshika Peninsula of Tōhoku, Japan, lasting approximately six minutes.〔 The earthquake was initially reported as 7.9 Mw by the USGS before it was quickly upgraded to 8.8 Mw, then to 8.9 Mw, and then finally to 9.0 Mw.〔 Sendai was the nearest major city to the earthquake, 130 km (81 mi) from the epicenter; the earthquake occurred 373 km (232 mi) from Tokyo.〔 The main earthquake was preceded by a number of large foreshocks, with hundreds of aftershocks reported. One of the first major foreshocks was a 7.2 Mw event on 9 March, approximately 40 km (25 mi) from the epicenter of the 11 March earthquake, with another three on the same day in excess of 6.0 Mw.〔 Following the main earthquake on 11 March, a 7.4 Mw aftershock was reported at 15:08 JST (6:06 UTC), succeeded by a 7.9 Mw at 15:15 JST (6:16 UTC) and a 7.7 Mw at 15:26 JST (6:26 UTC). Over eight hundred aftershocks of magnitude 4.5 Mw or greater have occurred since the initial quake, including one on 26 October 2013 (local time) of magnitude 7.1 Mw. Aftershocks follow Omori's Law, which states that the rate of aftershocks declines with the reciprocal of the time since the main quake. The aftershocks will thus taper off in time, but could continue for years.〔 One minute before the earthquake was felt in Tokyo, the Earthquake Early Warning system, which includes more than 1,000 seismometers in Japan, sent out warnings of impending strong shaking to millions. It is believed that the early warning by the Japan Meteorological Agency (JMA) saved many lives. The warning for the general public was delivered about 8 seconds after the first P wave was detected, or about 31 seconds after the earthquake occurred. However, the estimated intensities were smaller than the actual ones in some places in Kanto and Tohoku regions. This was thought to be because of smaller estimated earthquake magnitude, smaller estimated fault plane, shorter estimated fault length, not having considered the shape of the fault, etc. There were also cases where large differences between estimated intensities by the Earthquake Early Warning system and the actual intensities occurred in the aftershocks and triggered earthquakes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2011 Tōhoku earthquake and tsunami」の詳細全文を読む スポンサード リンク
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