The global seismographic network reveals atmospherically coupled normal modes excited by the 2022 Hunga Tonga Eruption

Ringler, AT, Anthony, RE, Aster, RC, Taira, T, Shiro, BR, Wilson, DC, De Angelis, S ORCID: 0000-0003-2636-3056, Ebeling, C, Haney, M, Matoza, RS
et al (show 1 more authors) (2023) The global seismographic network reveals atmospherically coupled normal modes excited by the 2022 Hunga Tonga Eruption. Geophysical Journal International, 232 (3). pp. 2160-2174.

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<jats:title>Summary</jats:title> <jats:p>The eruption of the submarine Hunga Tonga-Hunga Haʻapai (Hunga Tonga) volcano on January 15, 2022, was one of the largest volcanic explosions recorded by modern geophysical instrumentation. The eruption was notable for the broad range of atmospheric wave phenomena it generated and for their unusual coupling with the oceans and solid Earth. The event was recorded worldwide across the Global Seismographic Network (GSN) by seismometers, microbarographs, and infrasound sensors. The broadband instrumentation in the GSN allows us to make high fidelity observations of spheroidal solid Earth normal modes from this event at frequencies near 3.7 and 4.4 mHz. Similar normal modes reported following the 1991 Pinatubo (Volcanic Explosivity Index of 6) eruption and were predicted, by theory, to arise from the excitation of mesosphere-scale acoustic modes of the atmosphere coupling with the solid Earth. Here, we compare observations for the Hunga Tonga and Pinatubo eruptions and find that both strongly excited the Earth normal mode 0S29 (3.72 mHz) and that the modal amplitude was roughly 11 times larger for the 2022 Hunga Tonga eruption. Estimates of attenuation (Q) for 0S29 across the GSN from temporal modal decay give Q = 332 ± 101, which is higher than estimates of Q for this mode using earthquake data (Q = 186.9 ± 5; Dziewonski &amp; Anderson 1981). Two microbarographs located at regional distances (&amp;lt; 1000 km) to the volcano provide direct observations of the fundamental acoustic mode of the atmosphere. These pressure oscillations, first observed approximately 40 minutes after the onset of the eruption, are in phase with the seismic Rayleigh wave excitation and are recorded only by microbarographs in proximity (&amp;lt; 1500 km) to the eruption. We infer that excitation of fundamental atmospheric modes occurs within a limited area close to the site of the eruption, where they excite select solid Earth fundamental spheroidal modes of similar frequencies that are globally recorded and have a higher apparent Q due to the extended duration of atmospheric oscillations.</jats:p>

Item Type: Article
Uncontrolled Keywords: Acoustic properties, Seismic instruments, Surface waves and free oscillations, Volcano seismology
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 31 Aug 2022 09:41
Last Modified: 09 Mar 2023 05:29
DOI: 10.1093/gji/ggac284
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