Simulation and inversion of harmonic infrasound from open-vent volcanoes using an efficient quasi-1D crater model

Watson, Leighton M.; Dunham, Eric M.; Johnson, J. B.

doi:10.1016/j.jvolgeores.2019.05.007

Cited by 22 publications

(43 citation statements)

References 39 publications

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“…Attenuation occurs through the radiation of acoustic waves to the atmosphere. The quality factor depends on crater geometry due to the acoustic impedance contrast at the outlet (see Watson et al., 2019). In the frequency domain, a low‐quality factor corresponds to a broad spectral peak.…”

Section: Harmonic Volcano Infrasound Signalsmentioning

confidence: 99%

“…Watson et al. (2019) developed a numerical model, CRes (Watson, 2019), that simulates the crater acoustic response for quasi‐1‐D crater geometries. CRes simulates the entire amplitude spectra and can be used to provide additional constraints on crater geometry and eruption properties.…”

Section: Cres Modelmentioning

confidence: 99%

“…The inversion scheme used here was first presented in Watson et al. (2019) and is a Markov chain Monte Carlo (MCMC) style inversion scheme. The steps for the i th iteration are shown below: Take a random step in all parameter directions to calculate a vector of proposed parameter values:

{\overset{x}{true}}_{i}^{*} = \frac{{\overset{x}{true}}_{i - 1}}{{\overset{x}{true}}_{0}} + {\overset{h}{true}}_{i - 1} normalΔ x,

where

{\overset{x}{true}}_{i}^{*}

is the vector of proposed parameter values,

{\overset{x}{true}}_{i - 1}

is the vector of parameter values at the previous iteration, and

{\overset{x}{true}}_{0}

is the initial estimate.…”

Section: Inverting For Crater Geometrymentioning

confidence: 99%

“…The amplitude increased (Figure 1), the peak frequency decreased, and the quality factor, which can be a proxy for crater resonance, increased after the onset of flank eruption (Figure 2). Previous studies have linked crater geometry to the characteristics of harmonic infrasound signals recorded at open‐vent volcanoes (e.g., Fee et al., 2010; Johnson & Watson, 2019; Johnson et al., 2018; Richardson et al., 2014; Watson et al., 2019). Following previous work at Mount Etna by Sciotto et al.…”

Section: Introductionmentioning

confidence: 99%

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Changes in Crater Geometry Revealed by Inversion of Harmonic Infrasound Observations: 24 December 2018 Eruption of Mount Etna, Italy

Watson

Johnson

Sciotto

et al. 2020

Geophysical Research Letters

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In December 2018, Mount Etna (Italy) experienced a period of increased eruptive activity that culminated in a fissure eruption on the southeast flank. After the onset of the flank eruption, the peak frequency of the summit infrasound signals decreased while resonance increased. We invert infrasound observations for crater geometry and show that crater depth and radius increased during the eruption, which suggests that the flank eruption drained magma from the summit and that eruptive activity led to erosion of the crater wall. By inverting the entire infrasound amplitude spectra rather than just the peak frequency, we are able to place additional constraints on the crater geometry and invert for, rather than assume, the crater shape. This work illustrates how harmonic infrasound observations can be used to obtain hightemporal-resolution information about crater geometry and can place constraints on complex processes occurring in the inaccessible crater region during eruptive activity. Plain Language Summary Volcanoes generate low-frequency sound waves in the atmosphere (infrasound) that can be recorded by specialized microphones. Much like giant musical instruments, the character of the sound can depend upon the shape and size of the crater. Mount Etna erupted in December 2018 with lava flowing out a fissure on the flank of the volcano. The character of the sound changed after the flank eruption. We study the change in the character of the sound in order to estimate how the shape of the volcanic crater at the summit of Mount Etna changed. Our results show that the crater got deeper and wider, which suggests that the eruption of lava on the flank of the volcano drained magma from the summit area. This work shows how infrasound observations can track changes in crater geometry and provide insight about the magma plumbing systems beneath volcanoes.

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Section: Harmonic Volcano Infrasound Signalsmentioning

confidence: 99%

Section: Cres Modelmentioning

confidence: 99%

{\overset{x}{true}}_{i}^{*} = \frac{{\overset{x}{true}}_{i - 1}}{{\overset{x}{true}}_{0}} + {\overset{h}{true}}_{i - 1} normalΔ x,

where

{\overset{x}{true}}_{i}^{*}

is the vector of proposed parameter values,

{\overset{x}{true}}_{i - 1}

is the vector of parameter values at the previous iteration, and

{\overset{x}{true}}_{0}

is the initial estimate.…”

Section: Inverting For Crater Geometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Changes in Crater Geometry Revealed by Inversion of Harmonic Infrasound Observations: 24 December 2018 Eruption of Mount Etna, Italy

Watson

Johnson

Sciotto

et al. 2020

Geophysical Research Letters

Self Cite

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“…The reclined S shape of N shows that spectral power is transferred away from the peak source frequency at 10-20 kHz ( N < 0) to higher frequencies at which N >0. Figures are reproduced from Reichman et al (2016) and Miller and Gee (2018) with permission. 2018; Watson et al, 2019), and source directivity (Jolly et al, 2017;Kim et al, 2012). Therefore, improved understanding of near-source distortions can lead to more accurate estimates of volcano-acoustic source characteristics.…”

Section: Introductionmentioning

confidence: 99%

Investigating Spectral Distortion of Local Volcano Infrasound by Nonlinear Propagation at Sakurajima Volcano, Japan

et al. 2020

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Sound waves generated by erupting volcanoes can be used to infer important source dynamics, yet acoustic source‐time functions may be distorted during propagation, even at local recording distances ( <15 km). The resulting uncertainty in source estimates can be reduced by improving constraints on propagation effects. We aim to quantify potential distortions caused by wave steepening during nonlinear propagation, with the aim of improving the accuracy of volcano‐acoustic source predictions. We hypothesize that wave steepening causes spectral energy transfer away from the dominant source frequency. To test this, we apply a previously developed single‐point, frequency domain, quadspectral density‐based nonlinearity indicator to 30 acoustic signals from Vulcanian explosion events at Sakurajima Volcano, Japan, in an 8‐day data set collected by five infrasound stations in 2013 with 2.3‐ to 6.2‐km range. We model these results with a 2‐D axisymmetric finite‐difference method that includes rigid topography, wind, and nonlinear propagation. Simulation results with flat ground indicate that wave steepening causes up to ∼2 dB (1% of source level) of cumulative upward spectral energy transfer for Sakurajima amplitudes. Correction for nonlinear propagation may therefore provide a valuable second‐order improvement in accuracy for source parameter estimates. However, simulations with wind and topography introduce variations in the indicator spectra on order of a few decibels. Nonrandom phase relationships generated during propagation or at the source may be misinterpreted as nonlinear spectral energy transfer. The nonlinearity indicator is therefore best suited to small source‐receiver distances (e.g., <2 km) and volcanoes with simple sources (e.g., gas‐rich strombolian explosions) and topography.

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Infrasound Radiation from Impulsive Volcanic Eruptions: Nonlinear Aeroacoustic 2D Simulations

Watson¹,

Dunham

Mohaddes

et al. 2021

Preprint

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Simulation and inversion of harmonic infrasound from open-vent volcanoes using an efficient quasi-1D crater model

Cited by 22 publications

References 39 publications

Changes in Crater Geometry Revealed by Inversion of Harmonic Infrasound Observations: 24 December 2018 Eruption of Mount Etna, Italy

Changes in Crater Geometry Revealed by Inversion of Harmonic Infrasound Observations: 24 December 2018 Eruption of Mount Etna, Italy

Investigating Spectral Distortion of Local Volcano Infrasound by Nonlinear Propagation at Sakurajima Volcano, Japan

Infrasound Radiation from Impulsive Volcanic Eruptions: Nonlinear Aeroacoustic 2D Simulations

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