NUMERICAL SIMULATION OF TSUNAMI INUNDATION IN OKAYAMA CITY CONSIDERING OCCURRENCE OF NANKAI TROUGH EARTHQUAKE

Nankai Trough earthquake is a massive earthquake which is estimated to occur in the near future in Japan. The elevation of vast reclaimed area located in the southern part of Okayama city is very low and the risk of liquefaction there is rather high. Therefore, an earthquake-triggered liquefaction and a severe tsunami inundation disaster are expected there. But, detailed information about tsunami inundation process on the land still has not been clarified at present state. In order to contribute to take evacuation countermeasures of Okayama city against tsunami inundation, 2-D tsunami inundation simulation was carried out. To clarify the tsunami inundation process, different numerical conditions of tsunami wave height and with or without a coastal levee's subsidence caused by liquefaction were investigated. Numerical results show that the levee's subsidence have a great influence on the expansion of tsunami inundation area. And the tsunami inundation progresses gradually in more than several hours by not only the first arrival of tsunami wave but also the second wave or coming several waves after.