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Solid Earth–atmosphere Interaction Forces During the 15 January 2022 Tonga Eruption

Description: 

Very large volcanic eruptions are rare, catastrophic events, for which modern geophysical observations can reveal energy and mass flux between the solid Earth and atmosphere. Only a few events such as the 1980 Mount St. Helens and 1991 Pinatubo eruptions have generated globally observed teleseismic body waves and/or long-period surface waves that constrain the space-time force histories from the eruptive process and coupled atmosphere-solid Earth interactions. On January 15, 2022 a series of powerful phreatomagmatic explosions at the Hunga Tonga-Hunga Ha’apai (HTHH) volcano sent an eruptive plume 58 km into the mesosphere, presenting an excellent opportunity to take advantage of extensive modern geophysical observations to study the eruptive process. In this work, we examine the source force system of the HTHH eruption as well as solid Earth-atmosphere interactions by analyzing long-period regional surface waves and teleseismic body waves directly excited by the eruption process. The source process is likely associated with pressure drop in the magmatic reservoir, and reaction forces to the ejection jet as erupted material vents to the atmosphere must occur. The latter process is more seismogenic than the related implosive process, so we assume a surface vertical point-force to deconvolve and model the seismic wavefield for periods less than 100 s. A simulated annealing non-linear inversion for a vertical source provides a complex force time history, F(t), which is in good agreement with estimates of F(t) from deconvolutions of stacked body waves and stacks of surface wave deconvolutions. Overall, the seismic observations are well-explained by a single force reaction to the explosion sequence which lasted ~4.2 hrs. The explosive stage was composed of multiple pulses (explosions) with peak magnitude of the vertical forcing of ~ 2 x 1013 N. Estimates of energy and mass flux through the process will be presented. Atmospheric acoustic standing waves near the source produced oscillatory peak forces of ~ 4 x 1014 N, exciting monochromatic Rayleigh waves in the solid Earth with peak frequencies of 3.7 and 4.6 mHz.

Session: Seismology's Role in Assessing Volcanic Hazard at Multiple Time Scales

Type: Oral

Date: 4/18/2023

Presentation Time: 10:15 AM (local time)

Presenting Author: Ricardo Garza-Giron

Student Presenter: No

Invited Presentation: Yes

Authors