2013 Volume 5 Issue 4 Pages 241-250
To estimate the magnitude of the 869 Jogan tsunami (described in the historical record), we surveyed tsunami deposits and constructed a source-fault model by combining geological data with geophysical simulation. Although the 2011 Tohoku earthquake was larger than the earthquake estimated by our Jogan model, the 2011 earthquake proved that tsunami deposits are evidence of past giant tsunamis, and reliable warnings of future giant tsunamis. Our study results on the Jogan tsunami were submitted to the Headquarters of Earthquake Research Promotion, and in March 2011, the evaluation was near completion. However, the earthquake occurred just before issuing a warning against a giant tsunami. We need to announce our study of ancient earthquakes and tsunamis to society as quickly as we can so as not to repeat such a tragedy. Moreover, we have to concurrently carry out reliable studies based on rigorous surveys.
