McKee, KathleenFee, DavidYokoo, AkihikoMatoza, Robin S.Kim, Keehoon2023-01-112023-01-112017-06-21McKee, Kathleen, et al. “Analysis of gas jetting and fumarole acoustics at Aso Volcano, Japan” Journal of Volcanology and Geothermal Research 340 (15 June 2017): 16-29. https://doi.org/10.1016/j.jvolgeores.2021.107381.https://doi.org/10.1016/j.jvolgeores.2017.03.029http://hdl.handle.net/11603/26628The gas-thrust region of a large volcanic eruption column is predominately a momentum-driven, fluid flow pro- cess that perturbs the atmosphere and produces sound akin to noise from jet and rocket engines, termed “jet noise”. We aim to enhance understanding of large-scale volcanic jets by studying an accessible, less hazardous fumarolic jet. We characterize the acoustic signature of ~2.5-meter wide vigorously jetting fumarole at Aso Vol- cano, Japan using a 5-element infrasound array located on the nearby crater. The fumarole opened on 13 July 2015 on the southwest flank of the partially collapsed pyroclastic cone within Aso Volcano's Naka-dake crater and had persistent gas jetting, which produced significant audible jet noise. The array was ~220 m from the fu- marole and 57.6° from the vertical jet axis, a recording angle not typically feasible in volcanic environments. Array processing is performed to distinguish fumarolic jet noise from wind. Highly correlated periods are charac- terized by sustained, low-amplitude signal with a 7–10 Hz spectral peak. Finite difference time domain method numerical modeling suggests the influence of topography near the vent and along the propagation path signifi- cantly affects the spectral content, complicating comparisons with laboratory jet noise. The fumarolic jet has a low estimated Mach number (0.3 to 0.4) and measured temperature of ~ 260 °C. The Strouhal number for infrasound from volcanic jet flows and geysers is not known; thus we assume a peak Strouhal number of 0.19 based on pure-air laboratory jet experiments. This assumption leads to an estimated exit velocity of the fumarole of ~79 to 132 m/s. Using published gas composition data from 2003 to 2009, the fumarolic vent area estimated from thermal infrared images, and estimated jet velocity, we estimate total volatile flux at ~ 160–270 kg/s (14,000–23,000 t/d)14 pagesen-USThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.Public Domain Mark 1.0http://creativecommons.org/publicdomain/mark/1.0/Text