2012 Volume 64 Issue 3 Pages 155-168
The 2011 off the Pacific coast of Tohoku Earthquake (Mw9.0) occurred on March 11, 2011, caused strong ground motion around northeastern Japan, and generated devastating tsunami, which killed more than 16,000 people. Before the strong ground motion hit cities, the Japan Meteorological Agency (JMA) issued Earthquake Early Warning (EEW) announcements to the general public of the Tohoku district and then the warning was automatically broadcast through TV, radios and cellular phone messages. JMA also issued the first tsunami warnings/advisories based on hypocentral parameters, i.e., location, focal depth and magnitude, at 14:49 (Japan Standard Time), which was about three minutes after the occurrence of the earthquake, and then upgraded them using sea-level observation data. This paper reports the performance of the EEW and the tsunami warnings/advisories, lessons learned from the earthquake, and direction for the improvement of the warning systems.