2:45 PM - 3:00 PM
[MIS11-05] Traces of Tsunami Caused by the 2024 Noto Peninsula Earthquake Recorded in Sea Surface Sediments off Iida Bay, Suzu City, Japan.
Keywords:Tsunami deposite, Noto Peninsula Earthquake, Marine sediment
The Noto Peninsula earthquake on January 1, 2024 triggered a tsunami and hit the northeastern part of the Noto Peninsula. The tsunami was found to run up to 5 m high, causing extensive damage to the Suzu City and Noto Town. While many studies have been conducted to understand the extent and scale of the tsunami damage on land, the impact on the coastal seafloor is less well understood. The sandy sediments in the shallow topography are considered denuded, suspended, and redeposited during the tsunami. Understanding the horizontal extent and depth distribution of the tsunami's impact on the seafloor is expected to contribute to estimation and simulation of tsunami.
In this study, we conducted five coastal sea surveys from three weeks to one year after the earthquake in the area east of Iida Bay (water depth: 5-300 m), and collected surface sediments at 25 sites using an Ashura corer. Three east-west transects were set up in a north-south direction, and differences in tsunami effects due to seafloor topography were examined. In addition, some sites were visited repeatedly for sediment sampling to capture changes in the sediments over time. The collected sediment cores were CT-imaged and described lithology and sediment structures to investigate tsunami impact on seafloor.
The sediment cores from some sites showed evidence of tsunami deposite. The differences in the sediment cores from the same depth at the three transects suggest that the microtopography of the seafloor may have influenced the tsunami impact differently. Furthermore, we observed that the parallel lamination formed by the tsunami were destroyed by bioturbation. Specifically, the parallel laminations observed in sediments collected in January and February 2024 were partially destroyed six months later and further destroyed one year later. This indicates that the benthic ecosystem is gradually recovering after tsunami impact.
In this study, we conducted five coastal sea surveys from three weeks to one year after the earthquake in the area east of Iida Bay (water depth: 5-300 m), and collected surface sediments at 25 sites using an Ashura corer. Three east-west transects were set up in a north-south direction, and differences in tsunami effects due to seafloor topography were examined. In addition, some sites were visited repeatedly for sediment sampling to capture changes in the sediments over time. The collected sediment cores were CT-imaged and described lithology and sediment structures to investigate tsunami impact on seafloor.
The sediment cores from some sites showed evidence of tsunami deposite. The differences in the sediment cores from the same depth at the three transects suggest that the microtopography of the seafloor may have influenced the tsunami impact differently. Furthermore, we observed that the parallel lamination formed by the tsunami were destroyed by bioturbation. Specifically, the parallel laminations observed in sediments collected in January and February 2024 were partially destroyed six months later and further destroyed one year later. This indicates that the benthic ecosystem is gradually recovering after tsunami impact.