Constraining a high-slip offshore fault area during the 2024 Noto Peninsula earthquake using tsunami inundation data and numerical simulations

The 2024 Noto Peninsula earthquake (Mw 7.5) caused significant tsunami inundation along the northeastern coast of the Noto Peninsula in Ishikawa Prefecture, Japan. To investigate the offshore slip distribution, we conducted field surveys and constructed a dataset of tsunami inundation depths. Using this dataset, we evaluated the performance of six previously proposed source fault models – developed based on crustal deformation and tsunami waveform data – in reproducing observed onshore tsunami inundation. Most of the models underestimated the tsunami inundation depth, likely due to insufficient constraints on the offshore slip amount resulting from limited geophysical observations. To address this issue, we introduced high-slip areas into offshore fault segments and tested multiple scenarios. This approach led to substantial improvements in model performance, with an appropriate scenario achieving a geometric mean (K) of 1.32 and a geometric standard deviation (κ) of 1.95. The substantial improvements in model performance demonstrate that tsunami inundation depth data provide a valuable complementary constraint for modeling offshore slip. This constraint is particularly important in areas where direct geophysical observations are scarce and key features of the slip distribution may otherwise go undetected.