Waveform inversion of acoustic-gravity waves during the 2023 eruption of Shishaldin volcano, Alaska
Matthew M. Haney1 , David Fee2, and John J. Lyons1
Affiliations: 1Alaska Volcano Observatory, U.S. Geological Survey Volcano Science Center, Anchorage, AK, USA; 2Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA
Presentation type: Talk
Presentation time: Friday 10:45 - 11:00, Room S160
Programme No: 2.1.5
Abstract
We report on low frequency signals, extending to periods as long as 22 minutes, observed on local infrasound sensors during the 2023 eruption of Shishaldin volcano in Alaska. Such signals have been identified globally following other large eruptions and we focus on high-quality recordings from one of the largest paroxysms during the months-long Shishaldin eruption (Event 11, starting ~13:35 UTC September 25, 2023). We observe peaks in the amplitude spectrum at 0.75 and 1.5 mHz (22 and 11 minutes period) after applying broadband instrument correction to data from an infrasound station ~6 km north of the vent. Analysis of radiosonde data from nearby Cold Bay, Alaska, indicates these signals are at or below the atmospheric buoyancy frequency and therefore we model the signals using acoustic-gravity theory. Assuming a mass source with a source-time-function given by a Gaussian located above the vent, we perform a grid search inversion based on waveform fitting for 2 parameters: the source elevation and time duration. We obtain good waveform fits, especially for the initial 20 minutes of the signal, for a source located 1.7 km above the vent. We estimate a peak mass eruption rate of 10^8 kg/s and, by integrating the source-time function, we find a total erupted mass of 4.3x10^8 kg. This erupted mass agrees to within a factor of 2 with an independent estimate based on satellite observations of sulfur-dioxide emissions and suggests acoustic-gravity waves can be used to estimate critical eruption source parameters in near real-time.