THE GREAT TOHOKU EARTHQUAKE IN JAPAN ON MARCH 11, 2011

Abstract

The earthquake with the moment magnitude of 9.0, which hit Japan on March 11, 2011, is among the five largest earthquakes in the world since 1900. Its effects reached the highest, seventh, grade on the Japan Meteorological Agency intensity scale. In the earthquake, 15,842 people died, 5,890 were injured and 3,485 were missing, mostly due to a large tsunami that reached the maximum run-up height of 40.5 metres. It is estimated that this was the most expensive natural disaster in the history of the world. The earthquake was caused by a sudden upthrow in the Japan deep-sea trench where the Pacific tectonic plate is subducting under the Okhotsk microplate. The rupture was about 500 kilometres long and 200 kilometres wide, with the thrusting of 5-8 metres. This is also the height of the sudden uplift of the sea bed, which caused the tsunami. Due to the earthquake, parts of Honshu moved towards the east for up to 2.4 metres. The earthquake shifted the Earth's rotation axis by 10-25 centimetres, due to the redistribution of masses, thus shortening the day by 1.8 microseconds. Due to the damaged reactors of the Fukushima Nuclear Power Plant, the earthquake was followed by a nuclear crisis that lasted several months.