Lessons learned from the tsunami disaster caused by the 2011 Great East Japan Earthquake and improvements in JMA ' s tsunami warning system

A huge tsunami generated by the 2011 Great East Japan Earthquake (also known as the 2011 off the Pacific coast of Tohoku Earthquake) that struck at 14:46 JST (UTC+9) on March 11, 2011, hit a huge stretch of the Pacific coast of Japan and caused severe damage over an area extending from the Tohoku district to the Kanto district. In the aftermath of the disaster, the Japan Meteorological Agency (JMA) investigated the content and expressions of the tsunami warning bulletins released as well as the timing of their issuance in relation to this occurrence at that time. The results were used to support consideration of how tsunami warnings could be improved in their role as a type of disaster preparedness information to protect life. The investigation revealed several problems, including the underestimation of earthquake magnitude promptly determined after the quake which in turn caused the underestimation of forecast tsunami heights. Another issue was the inappropriate announcement of tsunami observations; all the observed tsunami heights were announced even while waves were still small, which caused some people to believe evacuation was unnecessary for what they thought was a minor tsunami. JMA’s tsunami warnings must be timely, easy to understand and useful for organizations related to disaster prevention. To overcome the problems found in the investigation and to better meet these requirements, JMA improved the approach used in its tsunami warning system and enhanced the content and expressions of bulletins so that warnings urge people to evacuate as appropriate. As part of such improvements, JMA also remains active in its awareness-raising efforts as a key area in the appropriate usage of warnings and successful evacuation. Based on these activities, JMA introduced a new tsunami warning system on March 7, 2013.