Detecting submarine landslides caused by the 2024 Noto Peninsula Earthquake through repeat bathymetric surveys in Toyama Bay, Japan

Abstract On January 1, 2024, an earthquake of magnitude 7.6 struck the Noto Peninsula in Ishikawa Prefecture, Japan. Tsunamis were recorded along nearby coasts following the earthquake, with the early tsunami arrival time at the Toyama tide station—located far from the earthquake epicenter—indicating potential submarine landslides in Toyama Bay. To identify these potential submarine landslides by detecting changes in seafloor depth, we collected new bathymetric data using a multibeam echo sounder in January and February 2024, and then compared them with data collected in 2010. This bathymetric comparison revealed submarine landslides along a submarine canyon off the Jinzu River, covering an area measuring 3.5 km × 1 km at depths of 40–370 m. Slide relief ranged from several meters up to 40 m, with some slides displaying distinct head scarps. Seafloor observations in areas with minor depth changes confirmed the presence of cliffs, disturbed seabed, and a redox boundary on the disturbed oxide layer, indicating recent landslides. Given the slide distribution within the estimated tsunami source area of the 2024 Noto Peninsula Earthquake, it is likely these slides were triggered by the earthquake.