| At 2:46 p.m. (JST) on March 11, 2011, The 2011 off the Pacific coast of Tohoku Earthquake (hereinafter referred to as ”The 2011 Tohoku Earthquake”) occurred, striking mainly the Tohoku region of northeastern Japan and causing devastating damage. The number of dead or missing had exceeded 23 000 by the end of May 2011. At the many dams where earthquake motion at or above a specified level was observed, special safety inspections were immediately carried out by each dam manager and the results were reported to the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). Among the dams constructed on rock foundation under the regulation, “Cabinet Order Concerning Structural Standard for River Administration Facilities, etc.”, there were no dams with severe damages in spite of the massive scale of the earthquake. However, an old earthfill embankment of an irrigation pond, which was constructed more than 60 years ago and located outside of regulated areas under the River Law, breached due to the earthquake . This report outlines the results of special safety inspections reported by the dam managers, detailed in-situ investigations of the dams in the jurisdiction of the MLIT carried out by the MLIT and the Public Works Research Institute (PWRI), and the characteristics of the earthquake motions recorded at these dams. |
