The tsunami caused by the 2011 Tohoku earthquake resulted in a severe accident at the Fukushima Daiichi nuclear power plant (NPP). In light of analysis of the generation mechanisms of the earthquake and tsunami, a tsunami source model is inferred and further verified by the seismic source model inferred from ground motions. Distribution of large slip in the area along the Japan trench is a common finding obtained from both models. Through simulation analysis of the observed tsunami at the NPP sites, it becomes clear that the large slip in the shallow area along the Japan Trench, the time difference of rupture propagation, and the time delay of tsunami propagation are the main factors that significantly affect the tsunami heights.

Tohoku Earthquake on March 11, 2011 occurred at the plate boundary between the Pacific and North America plates along the Japan Trench, generating the destructive tsunami. Because it has been thought that these inter plate earthquakes happen repeatedly at similar magnitude and location in an almost fixed time interval, the occurrence of Tohoku Earthquake Tsunami which exceeds the maximum magnitude of historical earthquake tsunami records for the past hundreds of years could not be predicted. Which means that, in the probabilistic tsunami hazard assessment for the future prediction, it is necessary to apply a different concept from existing scenario tsunami assessment based on the maximum magnitude of historical earthquake tsunami. As a new modeling method for scenario tsunami, we propose a characterized tsunami source model which indicates setting method of tsunami source area and slip distribution by inter plate earthquake. Moreover, uncertainty (β) of tsunami simulation using the characterized model is analyzed, and improvement of the accuracy for modeling concerning the characteristic on tsunami source or the run-up characteristic shows that β can be reduced rather than past knowledge.

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In the area in front of Nankai trough, tsunami wave height may increase if tsunamis attacking from some wave sources overlap because of time-lag of seismic event on Nankai trough. To evaluation tsunami risk of the important facilities located in front of Nankai trough, we proposed the probabilistic tsunami hazard assessment considering uncertainty on time-lag of seismic event on Nankai trough and we evaluated the influence that the time-lag gave to tsunami hazard at the some representative points.

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