A Composite Seismic Source Model for the First Major Event During the 2022 Hunga (Tonga) Volcanic Eruption

The violent eruption of the Hunga (Tonga) submarine volcano on 15 January 2022 caused a 58 km-heigh ash plume, catastrophic tsunami, and significant global seismic and infrasound waves. However, the physical mechanism underpinning its multiple-explosive events remains unclear, and its resolvability relies on the seismic waveform source inversion. The studies of two different point-source models, the seismic moment tensor (MT) and the single force (SF), have been performed separately for this eruption, which, interestingly, can explain the seismic data adequately. Here, we use a joint inversion of MT and SF to unravel a composite source of an explosion-like MT and a significant upward force for the first major explosive event. Regarding the direction and magnitude, we propose that the upward force is likely a rebound force in response to the pressure drop on the seafloor because the water body above the volcano was abruptly uplifted by the shallow underwater explosion.