Author(s): Kenta Kudai; Keisuke Yoshida; And Shiro Maeno
Linked Author(s): Keisuke Yoshida
Keywords: Nankai Trough earthquake; Tsunami inundation; Nonlinear shallow water equations; Liquefaction
Abstract: A Nankai Trough earthquake is a strong continuous earthquake that is predicted to occur in the Pacific Ocean off the coast of western Japan in the near future. Consequently, if such an earthquake were to occur, a large tsunami above-2 m class is predicted to strike in Okayama city, located in the Chugoku Region of Japan, facing the serene Seto Inland Sea. The elevations of vast reclaimed land areas located in the southern part of the city are extremely low, and the risk of liquefaction there is rather high. Therefore, earthquake-triggered liquefaction and a severe tsunami inundation disaster are predicted to occur there. Nevertheless, outcomes and conditions related to the tsunami inundation process on the land have remained unclear. To contribute to countermeasures of the city against tsunami inundation by clarifying the process, 2-D numerical tsunami simulation was conducted. Four cases of analyses were conducted considering the possibilities of arrival of larger waves than the estimated ones and coastal levee’s subsidence caused by liquefaction. Numerical results show that the levee’s subsidence has a great influence on the tsunami inundation area expansion. Furthermore, the tsunami inundation progresses gradually, taking a long time with several waves.