10:45 AM - 11:00 AM
[HDS06-11] Estimating the Scale of Past Submarine Landslide Tsunamis in the Sea of Japan
Keywords:submarine landslide, tsunami, The Sea of Japan
The Sea of Japan contains traces of submarine landslide collapses of various sizes, some of which may have caused tsunamis in the past. Many important infrastructure facilities are located in coastal areas of Japan. Therefore, it is very important for disaster prevention to estimate the risk of tsunamis caused by submarine landslides that may occur in the future. The objective of this study is to establish a method for estimating the magnitude of tsunamis generated along the Sea of Japan coast using trace data from past submarine landslides.
We examined data from about 1,500 submarine landslide sites in the Sea of Japan and were able to extract about 300 sites whose longitudinal profiles clearly had the shape of landslides. For the extracted submarine landslide sites, the volume of the landslide mass was estimated from their shapes. Then, using parameters such as water depth, slope angle, landslide width, and volume, the initial tsunami characteristic amplitude, which is the maximum depression of the free surface above the submarine landslide, can be calculated. In this study, the equation of Watts et al. (2005) was used to estimate the scale of tsunamis caused by submarine landslides.
As a result, the tendency of tsunamis caused by submarine landslides varies from region to region. Large-scale tsunamis with initial amplitudes exceeding 10 m in tsunami characteristics were found to be concentrated in southwestern Hokkaido, while medium-scale tsunamis with amplitudes exceeding 1 m were found to be distributed over a wide area. In the Sea of Japan, submarine active faults are distributed in the relatively shallow part of the continental shelf, and these seismic activities may have affected the occurrence of submarine landslides. It is expected that a probabilistic model will be developed based on the data employed in the analysis of this study, and that a method will be developed to estimate submarine landslide tsunami hazards that may occur in the future.
Acknowledgments
This study was supported by JSPS Grant-in-Aid for Scientific Research 22H01606. In addition, Takashi Kumamoto (Okayama University) provided data on the submarine landslide traces for the writing this report.
We examined data from about 1,500 submarine landslide sites in the Sea of Japan and were able to extract about 300 sites whose longitudinal profiles clearly had the shape of landslides. For the extracted submarine landslide sites, the volume of the landslide mass was estimated from their shapes. Then, using parameters such as water depth, slope angle, landslide width, and volume, the initial tsunami characteristic amplitude, which is the maximum depression of the free surface above the submarine landslide, can be calculated. In this study, the equation of Watts et al. (2005) was used to estimate the scale of tsunamis caused by submarine landslides.
As a result, the tendency of tsunamis caused by submarine landslides varies from region to region. Large-scale tsunamis with initial amplitudes exceeding 10 m in tsunami characteristics were found to be concentrated in southwestern Hokkaido, while medium-scale tsunamis with amplitudes exceeding 1 m were found to be distributed over a wide area. In the Sea of Japan, submarine active faults are distributed in the relatively shallow part of the continental shelf, and these seismic activities may have affected the occurrence of submarine landslides. It is expected that a probabilistic model will be developed based on the data employed in the analysis of this study, and that a method will be developed to estimate submarine landslide tsunami hazards that may occur in the future.
Acknowledgments
This study was supported by JSPS Grant-in-Aid for Scientific Research 22H01606. In addition, Takashi Kumamoto (Okayama University) provided data on the submarine landslide traces for the writing this report.