Great East Japan Earthquake

The Japan Meteorological Agency named the event the 2011 off the Pacific coast of Tohoku Earthquake. Its epicentre lay about 130 km east-southeast of the Oshika Peninsula in Miyagi Prefecture at a depth of about 24 km. With a moment magnitude of 9.0 it was the largest earthquake recorded in Japan and one of the five largest worldwide since instrumental measurement began. The seafloor near the trench shifted by as much as 50 m, the Oshika Peninsula moved more than 5 m to the east-southeast, and parts of the coast subsided by around a metre, worsening later flooding.

Japan's strict building codes limited damage from the shaking itself, and the earthquake early warning system alerted millions of people seconds before strong motion arrived. Liquefaction damaged reclaimed land around Tokyo Bay, and a dam failure in Fukushima Prefecture caused deaths.

The tsunami was the main cause of death. Along the rias of the Sanriku coast in Iwate and northern Miyagi, narrow bays funnelled the waves to great heights; the highest run-up, about 40 m, was measured at Miyako in Iwate. On the flat plains of southern Miyagi and Fukushima the water penetrated several kilometres inland, flooding Sendai Airport. Seawalls built after earlier tsunamis were overtopped in many towns.

Communities such as Rikuzentakata, Ōtsuchi, Minamisanriku, Onagawa and parts of Ishinomaki were largely destroyed. At Ōkawa Elementary School in Ishinomaki, 74 pupils and 10 staff died after an evacuation was delayed – a tragedy that led to court rulings on schools' duty to prepare for disasters. By contrast, in Kamaishi nearly all schoolchildren survived because they had been trained to flee to high ground immediately.

The Fukushima Daiichi plant, operated by the Tokyo Electric Power Company (TEPCO), shut down automatically when the earthquake struck, but the tsunami, some 15 m high at the site, flooded the emergency diesel generators and electrical systems. Without cooling, the cores of reactors 1, 2 and 3 melted, and hydrogen explosions destroyed the buildings of units 1, 3 and 4. Radioactive material was released over parts of Fukushima Prefecture and beyond. The accident was rated at Level 7, the highest on the international scale, the same as Chernobyl.

The government ordered the evacuation of areas within 20 km of the plant and of more distant districts with high contamination; at the peak, well over 100,000 people from Fukushima Prefecture were displaced. Evacuation orders have since been lifted in most areas after decontamination, but some zones remain restricted, and many former residents have not returned. Decommissioning of the plant, including the removal of melted fuel, is expected to take decades. Independent investigations criticised TEPCO and regulators for underestimating the tsunami risk, and nuclear regulation was reorganised under a new Nuclear Regulation Authority in 2012. The accident also influenced energy policy abroad, including Germany's decision in 2011 to phase out nuclear power.

Japan's Self-Defence Forces mobilised about 100,000 personnel for rescue and relief, the largest operation in their history. Rescue teams and aid came from well over a hundred countries and regions, and United States forces supported relief efforts in Operation Tomodachi ('friend'). Volunteers from across Japan cleared debris and helped in evacuation centres. Rolling power cuts and shortages affected eastern Japan for weeks after the disaster.

The Reconstruction Agency was established in 2012 to coordinate recovery. Towns were rebuilt on raised ground or relocated to hills, massive new seawalls were built along much of the coast, and railways and roads, including the Sanriku Coastal Road, were reconstructed. The Sanriku Fukkō ('reconstruction') National Park was created in 2013 by expanding an existing park, and the Michinoku Coastal Trail links the coast from Aomori to Fukushima on foot.

The recovery has been uneven. Population decline, already under way before 2011, accelerated in many coastal towns, and some high seawalls have been criticised for cutting communities off from the sea. The disaster also brought deaths from the strain of evacuation, recognised officially as disaster-related deaths, especially among elderly evacuees in Fukushima.

Every year on 11 March a national memorial ceremony was held for the first ten years, and a moment of silence is observed across Japan at 14:46. Memorial parks, preserved ruins (shinsai ikō) such as the former Ōkawa and Arahama elementary schools, and museums along the coast form a network known as the 3.11 Densho Road, intended to pass on the lessons of the disaster.

The disaster led Japan to revise tsunami forecasting, evacuation planning and school disaster education, to build on the principle that people should flee first rather than rely on seawalls, and to reassess the safety of nuclear power. It also revived scholarly attention to historical tsunamis, such as the Jōgan tsunami of 869, which had flooded the same plains more than a thousand years earlier.