Estimating Crustal Velocity Structure in Alaska From Acoustic-to-Seismic Coupling From the 2022 Hunga Eruption, Tonga
Description:
The 2022 climactic eruption of the Hunga volcano in the Kingdom of Tonga generated broadband acoustic waves that were clearly observed over 10,000 kilometers away at numerous pressure sensors in Alaska. The University of Alaska Fairbanks and the Alaska Volcano Observatory operate over 150 stations in the state that are equipped with a single infrasound sensor, a colocated broadband seismometer, and a colocated barometer. The arrival of high-amplitude acoustic energy from the eruption at a regional network of colocated sensors provides a unique opportunity to examine acoustic-to-seismic coupling and to use these observations to estimate shallow elastic parameters in the Alaska region. We compute coherence between pressure and vertical seismic channels between 0.01 Hz and 2 Hz for all available colocated sites in Alaska and observe network-wide peaks and troughs in coherence. Notable troughs occur at around 0.2 Hz, and to a lesser extent, at 0.075 Hz. We interpret these troughs as interference imposed by the secondary and primary microseismic peaks on the relatively low-amplitude seismic signal from Tonga coupling. We compute coupling coefficients from seismic over acoustic amplitude ratios in passbands with high coherence, allowing us to relate acoustic-seismic coupling to bulk elastic parameters at different maximum crustal depths. We compare our results to existing shear-wave velocity estimates in Alaska, and observe good agreement, particularly for a depth of approximately two kilometers. Mean shear-wave velocity estimates from these derived elastic parameters provide an empirical dataset for investigating seismic site effects, station-specific velocity corrections, and augmenting Vs30 estimates for ground-motion modeling.
This work was supported by the Nuclear Arms Control Technology (NACT) Program at Defense Threat Reduction Agency (DTRA). Cleared for Release.
Session: Advancements in Forensic Seismology and Explosion Monitoring - III
Type: Oral
Date: 5/2/2024
Presentation Time: 02:45 PM (local time)
Presenting Author: Kenneth
Student Presenter: No
Invited Presentation:
Authors
Kenneth Macpherson Presenting Author Corresponding Author kamacpherson@alaska.edu University of Alaska Fairbanks |
David Fee dfee1@alaska.edu University of Alaska Fairbanks |
Juliann Coffey jrcoffey@alaska.edu University of Alaska Fairbanks |
Stefan Awender sawender@alaska.edu University of Alaska Fairbanks |
Bryant Chow bhchow@alaska.edu University of Alaska Fairbanks |
Sam Delamere swdelamere@alaska.edu University of Alaska Fairbanks |
Matthew Haney mhaney@usgs.gov U.S. Geological Survey |
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Estimating Crustal Velocity Structure in Alaska From Acoustic-to-Seismic Coupling From the 2022 Hunga Eruption, Tonga
Category
Advancements in Forensic Seismology and Explosion Monitoring