Scenario Tsunami Source Modeling and Probabilistic Tsunami Hazard Assessment Method


Abstract eng:
The tsunami caused by the 2011 off the Pacific Coast of Tohoku Earthquake on March 11, 2011 (the 2011 Tohoku Tsunami) led to a severe accident at the Fukushima Daiichi Nuclear Power Plant (NPP) of Tokyo Electric Power Company. The accident revealed the underestimation of the tsunami design level of the power plant, its unpreparedness for tsunamis exceeding the design level, and the importance of awareness of tsunami risks to NPPs. The tsunami design levels of NPPs in Japan have been estimated based on a report by the Japan Society of Civil Engineers (JSCE). In the JSCE report, a basic tsunami source models which can reproduce tsunamis in the past are established and various tsunami source models based on the basic tsunami source models are provided by changing the positions, strikes, dips, and so on. This estimation method has been applied to address the uncertainty of possible tsunamis in the future. It, however, failed to anticipate a tsunami height comparable to that of the 2011 Tohoku Tsunami. Consequently, the conventional method based on the greatest magnitude of earthquakes in the past proved inadequate in establishing the magnitude of possible earthquakes for the tsunami assumption. After the 2011 Tohoku Tsunami, Sugino et al.[1] compiled findings on tsunami sources triggered by M w 9-class earthquakes in Japan and abroad (including the 2011 Tohoku Tsunami) to improve scenario tsunami source modeling in future forecasts. The authors then proposed a characterized source model for tsunamis triggered by inter-plate earthquakes by adopting a different concept from the conventional tsunami assumption method based on the greatest scale of tsunami in the past while pointing out the undeniable possibilities of even greater tsunamis in the future. To improve the probabilistic tsunami hazard assessment method used in an evaluation of the tsunami risks at NPPs, this study applies the characterized source model by Sugino et al.[1] as a new scenario tsunami model to present practical examples of tsunami for the inter-plate earthquakes along the Chishima Trench and Japan Trench. The results are compared with tsunamis assumed by the conventional model (hereinafter called the “old scenario tsunami model”) in order to examine the impact of the different approaches in handling uncertainties for tsunami assumption in terms of the results of the probabilistic tsunami hazard assessment. As a result, the difference of the tsunami hazard curve before the 2011 Tohoku Tsunami was significantly large in a range smaller than 10-2 (annual exceedance probability) in case of water level rising. Comparison of the annual exceedance probability in terms of the peak water level based on the simulation analysis of the 2011 Tohoku tsunami demonstrated that the result based on the new scenario tsunami model (about 10-3) is roughly 103 times greater than the result based on the old scenario tsunami model (less than 10-6). This report is a summary of the studies of Sugino et al.[1,2], which were published in the Japan Association for Earthquake Engineering (JAEE) journal in Japanese.

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Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 1556.:
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