The Characterizing Model for Tsunami Source regarding the Inter-plate Earthquake Tsunami

Abstract

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.

Effects of the Model for Scenario Tsunami on the Probabilistic Tsunami Hazard Assessment

“…This section describes the procedure for applying the new model for scenario tsunami to PTHA, which is a part of the procedure for the PTHA described in Section 2.1 that is mainly related to the models developed for tsunami sources and earthquake activities. With respect to the tsunami source model, the characterization method for scenario tsunami by Sugino et al 4) is employed for the new model for scenario tsunami. More specifically, characteristics of tsunami sources are indicated in three levels-namely, outer fault parameters, inner fault parameters, and rupture process parameters.…”

“…In this manner, the new model for scenario tsunami makes a decisive departure from the conventional approach based on the largest magnitude of earthquakes in the past by using the characterization method for scenario tsunami proposed by Sugino et al 4) This approach enables us to take the possible occurrence of tsunamis exceeding the largest tsunami in the past into consideration.…”

“…Sugino et al 4) compiled findings on tsunami sources caused by moment magnitude (M w ) 9-class earthquakes around Japan and abroad (including the 2011 Tohoku Tsunami) to advance a model for scenario tsunamis. The authors then proposed a characterization method for scenario tsunamis caused by inter-plate earthquakes by adopting a different concept from the conventional scenario tsunamis based on the largest magnitude of tsunami in the past while pointing out the undeniable possibilities that future tsunamis may exceed the largest recorded magnitude.…”

“…The authors then proposed a characterization method for scenario tsunamis caused by inter-plate earthquakes by adopting a different concept from the conventional scenario tsunamis based on the largest magnitude of tsunami in the past while pointing out the undeniable possibilities that future tsunamis may exceed the largest recorded magnitude. Sugino et al 4) also demonstrated that the characterization method for scenario tsunami can be successfully applied to the 2011 Tohoku Tsunami to reproduce almost the same trace heights, and that the variation in tsunami height calculated by a numerical tsunami simulation model was relatively reduced to existing findings. Meanwhile, the Central Disaster Management Council 5) proposed a fault model for the greatest-class tsunamis caused around the Nankai Trough, and Seto et al 6) proposed numerous methods for multiple scenario tsunamis.…”

“…In order to contribute to the advancement of the PTHA used in the tsunami risk assessment for NPPs, this paper applies the characterization method for scenario tsunami by Sugino et al 4) as a new model for scenario tsunami devised after the 2011 Tohoku Tsunami to present practical examples of tsunamis triggered by inter-plate earthquakes along the Chishima-Japan Trench. The results are compared with scenario tsunamis using the conventional model based on the largest tsunami in the past (hereinafter, "old model for scenario tsunami") in order to examine the impact and effect of the different approaches in treating uncertainties of scenario tsunamis in terms of the PTHA results.…”