The Great East Japan Earthquake is the name given to the collective catastrophe of the earthquake that occurred on March 11 in the Pacific Ocean just off the coast of Japan's northeastern Tohoku Region, the powerful tsunami that followed it, and subsequent aftershocks. The following is an overview of the disaster.
The earthquake occurred at 14:46 JST, its epicenter approximately 130 km east-southeast of the Oshika Peninsula in Miyagi Prefecture, at a depth of approximately 24 km under water. It registered a magnitude of 9.0, the biggest earthquake in recorded history in Japan, and occurred along an offshore fault zone extending from Iwate Prefecture in the north to Ibaraki Prefecture in the south, a distance of approximately 450 km and 200 km from east to west.
It was the fourth most powerful earthquake in the world since 1900, about 45 times stronger than the Great Kanto Earthquake that devastated Tokyo in 1923, and about 1,450 times stronger than the Great Hanshin earthquake of 1995 in Japan's southwestern Hyogo Prefecture, which was equivalent to the Sumatra-Andaman earthquake of 2004 in the Indian Ocean off Sumatra.
The earthquake triggered powerful tsunami waves ranging from 10 to 40 meters in height and travelling inland up to 6 km, devastating the coastal area. The resulting liquefaction, sunken ground, and collapse of dams and other infrastructure cut electricity, gas and water supplies in both the Tohoku and Kanto regions. The Pacific coast fishery and farming suffered damage estimated by the national government in the range of 16 trillion to 25 trillion yen, or up to 320 billion dollars.
Compounding the disaster was the loss of power and subsequent meltdown of nuclear reactors at the Fukushima Daiichi Nuclear Power Station. Without power, the system for cooling the reactors came to a halt, leading to the release of large quantities of radioactive contaminants. This required the immediate evacuation of residents living around the plant, and further evacuations as the contamination spread.