Observations from two studies of the January 2022 volcanic eruption of Hunga volcano, Tonga, show a complex main event that was as energetic as the 1883 Krakatau eruption, one of the deadliest and most destructive volcanic events in recorded history. The observations also uncover that the tsunami generated by this eruption was partially driven by an unexpected atmospheric wave. This set of observations will be helpful for disentangling the event and understanding the propagation of waves through the atmosphere and ocean. On 15 January, 2022, a massive volcanic eruption occurred on a small, uninhabited island in the South Pacific, Hunga Tonga-Hunga Ha‘apai. The Hunga Tonga eruption was one of the most powerful recorded, with audible sound detected over 10,000 kilometers from the source. In one study, Robin Matoza et al. present infrasound and seismic recordings, along with other geophysical observations, that characterize this event. An atmospheric Lamb wave, characteristic of energetic atmospheric events, circled the planet four times and was similar to the 1883 Krakatau eruption. The eruption also generated long range infrasounds and ionospheric interations, along with global tsunamis. In a second study focused on the tsunamis, first waves from which arrived more than 2 hours earlier than expected for conventional tsunamis, Tatsuya Kubota and colleagues investigated the generation and propagation mechanisms of the tsunami “forerunner.” Typically, tsunamis generated by volcanic eruptions are created by water displacement from deformation and atmospheric pressure waves that travel at about the same velocity as the tsunami. Kubota et al. found that for the Hunga Tonga eruption, a different sort of atmospheric pressure wave – a Lamb wave – also contributed to tsunami propagations. This interaction resulted in tsunami waves arriving much earlier than expected. Future tsunami models should incorporate this phenomenon, the authors say.
Atmospheric waves and global seismoacoustic observations of the January 2022 Hunga eruption, Tonga
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