Investigation of a static source model for non-seismic tsunamis using waveform inversion: a case study of the 2018 Anak Krakatau event

SUMMARY This study investigates the effectiveness of inversion methods using tsunami waveforms to analyse volcanic tsunami sources, which are a type of non-seismic tsunami source. We focused on the 2018 Anak Krakatau tsunami triggered by a volcanic eruption. This study developed a static initial sea surface displacement model based on tsunami waveform inversion with data recorded at tide gauge stations using a Gaussian-shaped sea surface displacement for the unit source. A key characteristic of our model is that all initial velocity components of the tsunami were zero. We tested 12 scenarios for accuracy to determine the most plausible sea surface displacement. The optimal displacement model reasonably reproduced the observed tsunami waveforms. The calculated water volume at the initial sea surface displacement was reasonably consistent with the total collapse volume of the Anak Krakatau eruption by magnitude. These findings suggest that our approach to developing a static source model can effectively apply to non-seismic tsunami events. Although this approach offers simplified tsunami source modelling for tsunami estimation during volcanic eruptions with complex source dynamics, further validation is required for its application to other non-seismic tsunami events.