A surrogate-assisted nonlinear inversion of tsunami waveform and trace height: application to the 2024 Noto Peninsula earthquake in Japan

Abstract The strong nonlinearity of shallow-water deformation and tsunami run-up makes the application of the conventional inversion method to onshore tsunami records challenging. Additionally, many iterations of nonlinear tsunami simulations are required to capture the nonlinear characteristics of trace heights, which can be unfeasible. This study proposed a new approach for the nonlinear inversion of earthquake fault slips using tsunami trace height data. Instead of demanding simulations, a surrogate model was employed to reach a global optimum, which enabled the instantaneous estimation of the desired model output. The proposed method, which uses both tsunami waveforms and trace heights, was then applied to the 2024 Noto Peninsula earthquake in Japan. The results revealed a large slip of over 6 m offshore of the eastern Noto Peninsula. Our results demonstrate the potential of the new approach to complement coastal tsunami observations challenged by uncertainty and scarcity. Graphical Abstract