4:00 PM - 4:15 PM
[HDS11-13] The Impact of Submarine Landslides in Toyama Bay during the 2024 Noto Peninsula Earthquake Tsunami
Keywords:Toyama Bay, Submarine landslide, Numerical simulation, 2024 Noto Peninsula Earthquake Tsunami
At 4:10 PM on January 1, 2024, an M7.6 earthquake struck the Noto Peninsula, triggering a tsunami. Tsunami traces with heights of approximately 5 meters were observed in Suzu City and Noto Town. Additionally, about 80 centimeters of tsunami was recorded at a tide gauge station located at the mouth of the Jintsu River in Toyama Bay, over 80 kilometers away from the area of the epicenter, approximately three minutes after the earthquake occurred. Initially, the Japan Meteorological Agency predicted the tsunami arrival time for Toyama Prefecture to be 4:20 PM, but it arrived significantly earlier than this forecast.
Efforts to simulate the tsunami using numerical simulations based on earthquake fault models have been attempted, but reproducing the tsunami that arrived within three minutes has proven challenging. This has led to suggestions of alternative wave sources, distinct from earthquakes, such as submarine landslides. Following the earthquake, reports from fishermen indicated incidents such as the outflow of crab pots located in the deep sea around 800 to 1000 meters in Toyama Bay, damage to fixed nets, and impacts on coastal nets. Furthermore, underwater investigations by the Japan Coast Guard confirmed occurrences of slope collapses at submarine valley. These observations corroborate the occurrence of significant changes in the underwater topography of Toyama Bay. However, specific evaluations regarding which areas of submarine landslides triggered the tsunami have not been conducted.
In this study, multiple submarine landslide scenarios were assumed based on the underwater topography of Toyama Bay. Using a submarine landslide tsunami integrated model, simulations were attempted to reproduce the tsunami waveforms. After numerous trial-and-error scenarios, it was found that triggering simultaneous submarine landslides in underwater valleys approximately 2-3 km off the coast of the Jintsu River mouth and 1-2 km off the coast of Toyama Shinko Port could very well explain the wave patterns observed in Toyama and at the Fushiki Tide Station. However, a comparison with the investigation of tsunami trace heights conducted from the Ao district to Iwasehama revealed a slight underestimation when considering only the aforementioned submarine landslides. Therefore, further examination of scenarios considering submarine landslides off the coast of Himi Fishing Port on the western side of Toyama Bay was carried out to ensure consistency with the observed trace heights. As results, we concluded that the tsunami observed in Toyama Bay following the 2024 Noto Peninsula earthquake was amplified by multiple submarine landslides at underwater valleys.
Efforts to simulate the tsunami using numerical simulations based on earthquake fault models have been attempted, but reproducing the tsunami that arrived within three minutes has proven challenging. This has led to suggestions of alternative wave sources, distinct from earthquakes, such as submarine landslides. Following the earthquake, reports from fishermen indicated incidents such as the outflow of crab pots located in the deep sea around 800 to 1000 meters in Toyama Bay, damage to fixed nets, and impacts on coastal nets. Furthermore, underwater investigations by the Japan Coast Guard confirmed occurrences of slope collapses at submarine valley. These observations corroborate the occurrence of significant changes in the underwater topography of Toyama Bay. However, specific evaluations regarding which areas of submarine landslides triggered the tsunami have not been conducted.
In this study, multiple submarine landslide scenarios were assumed based on the underwater topography of Toyama Bay. Using a submarine landslide tsunami integrated model, simulations were attempted to reproduce the tsunami waveforms. After numerous trial-and-error scenarios, it was found that triggering simultaneous submarine landslides in underwater valleys approximately 2-3 km off the coast of the Jintsu River mouth and 1-2 km off the coast of Toyama Shinko Port could very well explain the wave patterns observed in Toyama and at the Fushiki Tide Station. However, a comparison with the investigation of tsunami trace heights conducted from the Ao district to Iwasehama revealed a slight underestimation when considering only the aforementioned submarine landslides. Therefore, further examination of scenarios considering submarine landslides off the coast of Himi Fishing Port on the western side of Toyama Bay was carried out to ensure consistency with the observed trace heights. As results, we concluded that the tsunami observed in Toyama Bay following the 2024 Noto Peninsula earthquake was amplified by multiple submarine landslides at underwater valleys.