Meteotsunami Observed in Japan Following the Hunga Tonga Eruption in 2022 Investigated Using a One-Dimensional Shallow-Water Model

On 15 January 2022, the volcano Hunga Tonga about 8000-km away from Japan explosively erupted. Following the eruption, tsunami-like sea-level fluctuations were observed in Japan, much earlier than expected based on the oceanic long-wave propagation from Tonga. By contrast, atmospheric pressure disturbance presumably due to the eruption was also observed about 30 minutes before the sea-level change. Therefore, the observed sea-level fluctuations can be considered as meteotsunamis forced by the pressure perturbation rather than tectonically forced by the eruption, but the mechanism is not yet fully understood. This study attempts to understand the nature of this meteotsunami by using a simple one-dimensional shallow-water model. The results show that the time and amplitude of the observed sea-level changes are consistent with the simulated sea-level changes forced by the atmospheric forcing. A set of experiments with different bathymetry profiles also reveals the importance of amplification due to near-Proudman resonance over deep basins and the shoaling effect over the continental slope, while extremely deep and narrow topography such as trenches is of second-order importance.