Developing estimating equations of fatality ratio based on surveyed data of the 2011 Great East Japan Tsunami

The 2011 Great East Japan tsunami caused a wide range of devastating tsunami with maximum tsunami height of 40 m and 19,000 casualties especially along the Tohoku coast of Japan. The purpose of this study is to develop estimating equations of fatality ratio from tsunami arrival time for future tsunami loss assessment and investigate the effect of two coastal topography types namely, Sanriku-ria coast and Sendai plain. In this study, fatality ratio was defined as number of fatality divided by total number of people in a small scale of towns along the shoreline and tsunami arrival time was calculated from TUNAMI modelling with nesting-grids of 1350 m, 450 m, 150 m, and 50 m. Then, linear and nonlinear regression analysis were performed to develop a relationship model between fatality ratio and tsunami arrival time. Based on the results, a strong correlation that fatality ratio decreases with longer arrival time was found in both Sanriku-ria coast and Sendai plain. For different coastal types, different distributions of fatality ratio with tsunami arrival time are observed, in which fatality ratio of Sendai plain is higher than that of Sanriku ria-coast at the same arrival time generally.