The Hunga Tonga–Hunga Ha’apai Eruption of 15 January 2022: Observations on the International Monitoring System (IMS) Hydroacoustic Stations and Synergy with Seismic and Infrasound Sensors

Abstract

Examination of the International Monitoring System (IMS) hydroacoustic data recorded during the 15 January 2022 eruption of the Hunga Tonga–Hunga Ha’apai (HTHH) volcano shows that the in-water hydroacoustic sensors recorded a long-duration (40 min) activity starting before and ending after the paroxysmal HTHH eruption at about 4:15 UTC. The main eruption at 4:15 UTC simultaneously generated low-frequency [0.001–0.05] Hz seismic body waves and large infrasound waves in the atmosphere, as well as a tsunami. The peak-to-peak pressure observed at the closest IMS station, IS22, 1850 km away from the source, was 340 Pa, dwarfing the largest previously observed record for the signal from the Chelyabinsk meteor. The infrasound waves included a Lamb wave containing periods at least up to 2000 s. The Lamb wave and tsunami are well recorded on infrasound and near-shore seismometers. The air wave generated a precursor tsunami ahead of the main tsunami, but we do not observe it on the hydroacoustic IMS network. The dispersive tail of the main tsunami is observed on four in-water hydroacoustic hydrophone stations, one of them as far as 16,120 km away in the Atlantic Ocean.

Solid Earth–atmosphere interaction forces during the 15 January 2022 Tonga eruption

“…S7) are observed in both results. These signals produced infrasound and hydroacoustic phases ( 8 , 41 ) and also match the timing of volcanic activity as observed in satellite imagery ( 42 ), suggesting that this was a secondary explosive stage of the 15 January 2022 eruptive period. The events identified as E 1 and E 3 are associated with widely recorded infrasound events ( 8 , 41 ), whereas E 2 is not.…”

“…These signals produced infrasound and hydroacoustic phases ( 8 , 41 ) and also match the timing of volcanic activity as observed in satellite imagery ( 42 ), suggesting that this was a secondary explosive stage of the 15 January 2022 eruptive period. The events identified as E 1 and E 3 are associated with widely recorded infrasound events ( 8 , 41 ), whereas E 2 is not. We believe that the reason E 2 is not associated with an infrasound arrival is that it only began ~200 s after E 1 , making it difficult to isolate in the dispersed infrasound signal and coda of the earlier event, whereas our high-resolution seismic data deconvolution and inversion clearly resolve the signals in E 2 .…”

“…We believe that the reason E 2 is not associated with an infrasound arrival is that it only began ~200 s after E 1 , making it difficult to isolate in the dispersed infrasound signal and coda of the earlier event, whereas our high-resolution seismic data deconvolution and inversion clearly resolve the signals in E 2 . Furthermore, there is evidence of E 2 producing an increase in signal-to-noise ratio at hydroacoustic stations around the world ( 41 ).…”

The 2022 Hunga-Tonga megatsunami: Near-field simulation of a once-in-a-century event

“…In space, the loci of MFCI explosions need not necessarily be the same as the sites where eruptive products vented. Hence, the timing, spatial extent, and strength of the eruptive events deduced from satellite and ground observations ( 8 , 15 , 16 , 39 – 42 ) may not jive with those same features of explosive events extracted from tsunami data. Our goal is to develop a plausible time history of explosive events that explain 118 observed wave runup measurements and the two available tide gauge records in Nuku’alofa, as illuminated by tsunami simulation.…”

“…Curious that the largest explosive event of the sequence falls nearly one-half hour after the largest eruptive events, which occurred between 4:15 and 4:30 UTC ( 9 , 12 , 13 , 37 ). Curious too is that the largest explosive event of the sequence has a negligible expression in the global teleseismic records ( 12 , 13 , 41 , 42 ). Perhaps Blast 5 was not the same phreatomagmatic explosion-driven detonation as Blasts 3 and 4?…”