Rebuilding Tohoku: A joint geophysical and economic framework for hazard mitigation

Japanese authorities face complex issues in reconstructing the Tohoku coast that suffered enormous damage from the tsunami generated by the M9.0 earthquake on 11 March 2011. The defenses should reduce economic losses, while improved warning and evacuations should reduce fatalities, as shown by the March experience. However, critics argue that in areas with small and decreasing populations it would be more efficient to relocate communities. Improvements should be forthcoming from more effective use of earthquake history information, the paleotsunami record, tsunami modeling, geodesy, and other technologies. Conceptually, society is playing a game against nature. Nature chooses tsunami heights, and society selects the strategy to minimize the total costs of tsunami losses plus mitigation costs. As in any game of chance, there is a need to maximize the expectation value by selecting the best strategy, given the limited ability to estimate the occurrence, and effects of future tsunamis.