The Tohoku Tsunami of 11 March 2011 was successfully identified and classified as Red alert by the GDACS system only when reliable and more correct estimations of the originating event have been provided to the system by the international seismological networks. Nevertheless the early analysis of the event by the comparison of the scenario calculations with the sea level could give important information on the real extent and impact of the Tsunami. The paper describe the response of the GDACS system and identify the lessons learned that determined changes in the logic and the procedures of the Tsunami calculations strategy.JRC.G.2-Global security and crisis managemen
