The 2011 earthquake off the Pacific coast of Tōhoku , often referred to in Japan as the Great East Japan Earthquake and also known as the 2011 Tohoku earthquake,and the 3.11 Earthquake, 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 70 kilometres east of the Oshika Peninsula of Tōhoku and the hypocenter at an underwater depth of approximately 30 km (19 mi).It was the most powerful known earthquake ever to have hit Japan, and the fifth most powerful earthquake in the world