Tsunami forerunner of the 2024 Noto Peninsula earthquake observed near the mouth of the Kurobe River, Japan

Abstract The 2024 Noto Peninsula earthquake occurred along the northern coast of the Noto Peninsula in Japan and generated a large tsunami. The earthquake also caused submarine landslides that generated local tsunamis in Toyama Bay. When large earthquakes occurred near the coast, tsunamis with various origins were generated in several cases. In the case of the 2024 Noto Peninsula earthquake, the tsunami simulation results showed that a steep slope off the southeastern coast of the Noto Peninsula with a large co-seismic horizontal displacement of the Noto Peninsula generated a short-wavelength negative tsunami. The negative tsunami propagated to the southeast as a forerunner of the main tsunami generated by the co-seismic vertical displacement and affected a limited coastal area with the mouth of the Kurobe River and Ikuji and Tanaka stations in Toyama Prefecture. Simulation results were reasonably consistent with time series extracted from a video recorded at the Kurobe River mouth and observed at the two stations. The amplitude of the observed and computed negative forerunner was approximately 30 cm, arriving at Tanaka about 10 min before the main tsunami. Based on these results, we conclude that the 2024 Noto Peninsula earthquake generated a small tsunami forerunner due to a combination of large horizontal displacement and complex bathymetry.