The 2011 Tohoku, Japan, earthquake and tsunami

Abstract

The 2011 Tohoku earthquake (magnitude 9.0) was the largest earthquake in Japan's history. It caused nearly 20 000 casualties, mostly from devastating tsunamis. The earthquake and tsunami also seriously damaged the Fukushima Dai-ichi nuclear power station (NPS), causing meltdown of the reactor, a hydrogen explosion, and the release of radioactive materials. The Japanese long-term forecast of large earthquakes failed to foresee the gigantic size of this earthquake, because it was based on a characteristic earthquake model and past historical data of a few centuries. Recently installed extensive land and marine geophysical observation networks have revealed huge seafloor displacement and details of earthquake fault motion. While the promptly issued tsunami warning saved many lives, several issues have been identified to further improve the tsunami warning system. Similar tsunami disasters have occurred in the past, but that experience was not fully utilised to reduce the 2011 disaster. The lessons learned include the importance of geophysical observations, improvement of long-term forecasting of earthquakes, effective tsunami warning, assessment for future tsunami hazard, and preparedness and education for infrequent hazards. A giant earthquake occurred off northern Honshu, Japan, on 11 March 2011. This earthquake, with magnitude M9.0, was the largest in Japan's history, and caused a devastating tsunami disaster (Fig. 24.1), as well as serious damage to the nearby Fukushima Dai-ichi NPS. The earthquake was officially named the ‘off the Pacific coast of Tohoku earthquake’ by the Japan Meteorological Agency (JMA), but abbreviated as the Tohoku (-oki) earthquake in scientific literature including this report. The Japanese Cabinet Office called the earthquake and tsunami disaster, including the NPS accident, ‘the Great East Japan Earthquake disaster’.