Compounding impacts of the earthquake and submarine landslide on the Toyama Bay tsunami during the January 2024 Noto Peninsula event

The January 2024 Noto Peninsula earthquake (Mw 7.6) generated a destructive tsunami in the Sea of Japan region. Locally, inside Toyama Bay, the tsunami arrived at the Toyama wave and tide gauges within 2–3 min of the earthquake. Such an early tsunami arrival is inconsistent with the epicentral distance of ∼60 km. The travel time of the earthquake-induced tsunami is anticipated to be around 20 min, which is confirmed through tsunami simulations. Based on spectral and wavelet analyses of the Toyama tide and wave gauge records, we found 5 min, 14 min, and 32 min dominant wave periods. The shorter wave periods of 5 and 14 min are likely associated with a submarine landslide due to their early arrivals, as evidenced in our wavelet analysis. We then identified a potential submarine landslide location using the tsunami back-propagated travel time technique and visual inspection of the bathymetric profile. Conducting several simulations and comparing simulated and observed waveforms, we identified a seafloor landslide length of approximately 3000 m located ∼4 km offshore Toyama City. Our combined earthquake-landslide source model better reproduces the tsunami observations, indicating the contribution of the submarine landslide to the January 2024 Noto Peninsula tsunami. •Earthquake source models cannot explain the early arrival of tsunami at Toyama city during the 2024 Noto Peninsula event.•An additional source is needed to approximate the observed tsunami at Toyama tide and wave gauges.•A submarine landslide of length ∼3000 km occurred 4 km offshore Toyama city potentially caused the early tsunami arrivals.•These findings suggest serious implications for future tsunami disaster mitigation in the region.