The Great East Japan Earthquake Tsunami on March 11, 2011, caused unprecedented damage mainly in northeast Japan. This paper introduces the characteristics of the tsunami and resultant damage. The mechanism of the breaching of coastal structures and the effect of surviving structures on damage reduction in land are discussed. Then, a two-level tsunami mitigation concept, proposed and adopted by a committee hosted by the Government for recovery and reconstruction, is introduced. Within this framework, coastal structures are required to be resilient to external forces exceeding the design level. Various technologies that have been developed based on experience and research after the tsunami are introduced.

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