Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

H (Human Geosciences ) » H-DS Disaster geosciences

[H-DS13] Tsunami and Tsunami Forecast

Tue. May 28, 2019 1:45 PM - 3:15 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Naotaka YAMAMOTO CHIKASADA(National Research Institute for Earth Science and Disaster Resilience), Hiroaki Tsushima(Japan Meteorological Agency), Tatsuya Kubota(National Research Institute for Earth Science and Disaster Resilience)

[HDS13-P13] Sediment Transport Modeling due to Tsunamis caused by the Nankai great earthquakes

*Takuya Saito1, Kei Yamashita2, Toshitaka Baba1 (1.Tokushima Univ., 2.Tohoku Univ.)

Keywords:Nankai Trough Earthquake, Sediment Transport software

Tsunami that comes to the area in shallow water causes massive erosion and deposition of the coastal area. This causes damage such as collapse of coastal structures, burial of routes and blockage of water intakes at power stations. In the 2011 Tohoku Region Pacific Offshore Earthquake, collapses of coastal levees and burial of routes were caused by scouring. Damage caused by sediment transport will be prolonged, affecting recovery activities after the disaster. On the other hand, for disaster mitigations, it is necessary to accurately investigate the earthquakes and tsunamis back to the past as much as possible in order to estimate the maximum size of the earthquake and tsunami. Tsunami sediments are important information in studies of the historical earthquakes. Therefore, we simulated sediment transport using a numerical model developed by Takahashi et al. (1999, 2000, and 2011) for the great Nankai earthquakes.

The first study area is Tachibana-Bay classified as an important port having the rias coast in Shikoku, the southwestern Japan. In the simulation results, erosions were predicted in the straits between the islands, at the tip of the cape, near the estuary of the river and near the coastal levees. Sediment depositions were predicted in the vicinity. The maximum changes in erosion and sediment were about 10 m, about 6 m, respectively, for the great Nankai earthquakes (Mw 9.1). These were about 6 m and about 2 m, respectively, for the 1707 Hoei earthquake.

The other study area is a pond near the Cape Kamoda where tsunami sediment was found in the sediment layer about 2000 years ago (Okamura et al, 2012). However, all simulations we conducted in this study did not deposit sediment into the pond.

Acknowledgments: We thank Dr. Takahashi for providing us with the sediment transport software. This research is supported by Grant-in-Aid for Scientific Research 15H05718.