Analysis of gas jetting and fumarole acoustics at Aso Volcano, Japan

McKee, Kathleen; Fee, David; Yokoo, Akihiko; Matoza, Robin S.; Kim, Kee Hoon

doi:10.1016/j.jvolgeores.2017.03.029

Cited by 34 publications

(32 citation statements)

References 41 publications

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“…We note here that these results may also be interpreted as an indication that nonlinear effects are insignificant for Sakurajima acoustic signals and that consequently the linear propagation assumption is reasonable for estimating source parameters such as volume and mass flux (e.g., Fee et al, ; Johnson & Miller, ; Kim et al, ) or gas exit velocity (e.g., Matoza et al, ; McKee et al, ; Woulff & McGetchin, ). However, the potential significance of nonlinear effects at Sakurajima is evidenced by observations of supersonic wave propagation (Ishihara, ; Yokoo & Ishihara, ) asymmetric pressure waveforms (e.g., Matoza et al, ), and acoustically based source parameters that underestimate (Johnson & Miller, ) or overestimate (Fee et al, ) values obtained by other methods.…”

Section: Discussionmentioning

confidence: 60%

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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Section: Discussionmentioning

confidence: 60%

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

et al. 2020

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“…Using an infrasound sensor elevated from the Earth's surface yields an unprecedented view of the acoustic wavefield from volcanic explosions, an idea proposed by Matoza et al (). We use a tethered aerostat to achieve the vertical sensor coverage, but some studies such as McKee et al () and Rowell et al () have used nearby topography for an improvement in vertical station coverage for a network around a volcano. Including the aerostat sensor in the inversions yielded a measurable increase in dipole strength that would have otherwise been unobservable, and shows the importance of both the vertical sensor coverage and multipole inversion.…”

Section: Discussionmentioning

confidence: 99%

“…Johnson et al () solved for a subvertical dipole orientation where sensors located on the crater rim were above the crater floor. Studies such as McKee et al () and Rowell et al () have taken advantage of surrounding topography for network deployments at Aso and Karymsky volcanoes, respectively, in order to improve vertical coverage of infrasound sensors; however, not all volcanoes have the advantage of nearby high relief topography. This study, for the first time, incorporates the vertical dipole component using acoustic data collected on a tethered aerostat, which has great flexibility for sensor location and may sample closer to a hypothetical vertical dipole axis.…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Acoustic Multipole Waveform Inversion at Yasur Volcano, Vanuatu

et al. 2019

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Acoustic waveform inversions can provide estimates of volume flow rate and erupted mass, enhancing the ability to estimate volcanic emissions. Previous studies have generally assumed a simple acoustic source (monopole); however, more complex and accurate source reconstructions are possible with a combination of equivalent sources (multipole). We deployed a high‐density acoustic network around Yasur volcano, Vanuatu, including acoustic sensors on a tethered aerostat that was moved every ∼15–60 min. Using this unique data set we invert for the acoustic multipole source mechanism using a grid search approach for 80 events to examine volume flow rates and dipole strengths. Our method utilizes finite‐difference time‐domain modeling to obtain the full 3‐D Green's functions that account for topography. Inversion results are compared using a monopole‐only, multipole (monopole and dipole), simulations that do not include topography, and those that use a subset of sensors. We find that the monopole source is a good approximation when topography is considered. However, initial compression amplitude is not fully captured by a monopole source so source directionality cannot be ruled out. The monopole solution is stable regardless of whether a monopole‐only or multipole inversion is performed. Inversions for the dipole components produce estimates consistent with observed source directionality, though these inversions are somewhat unstable given station configurations of typical deployments. Our results suggest that infrasound waveform inversion shows promise for realistic quantitative source estimates, but additional work is necessary to fully explore inversion stability, uncertainty, and robustness.

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“…Eruption directivity, where the energy and mass may be preferentially discharged from the conduit, has important hazardous consequences prompting public interest and research. Several examples of such directivity effects have been documented from visual (Lube et al, ), seismic (Kanamori & Given, ), infrasound (Jolly et al, ; McKee et al, ; Rowell et al, ), and GPS observations (Fournier & Jolly, ). Observed features of infrasonic records include seismoacoustic energy coupling and wave conversion (e.g., Johnson & Aster ; Ichihara et al, ), excitations from secondary source features such as jet turbulence (e.g., Matoza et al, ; Rowell et al, ), or distorted frequencies that may be ascribed to Doppler effects (Jolly et al, ).…”

Section: Introductionmentioning

confidence: 98%

Capturing the Acoustic Radiation Pattern of Strombolian Eruptions using Infrasound Sensors Aboard a Tethered Aerostat, Yasur Volcano, Vanuatu

Jolly

Matoza

Fee

et al. 2017

Geophysical Research Letters

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We obtained an unprecedented view of the acoustic radiation from persistent strombolian volcanic explosions at Yasur volcano, Vanuatu, from the deployment of infrasound sensors attached to a tethered aerostat. While traditional ground‐based infrasound arrays may sample only a small portion of the eruption pressure wavefield, we were able to densely sample angular ranges of ~200° in azimuth and ~50° in takeoff angle by placing the aerostat at 38 tethered loiter positions around the active vent. The airborne data joined contemporaneously collected ground‐based infrasound and video recordings over the period 29 July to 1 August 2016. We observe a persistent variation in the acoustic radiation pattern with average eastward directed root‐mean‐square pressures more than 2 times larger than in other directions. The observed radiation pattern may be related to both path effects from the crater walls, and source directionality.

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Analysis of gas jetting and fumarole acoustics at Aso Volcano, Japan

Cited by 34 publications

References 41 publications

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

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

Three‐Dimensional Acoustic Multipole Waveform Inversion at Yasur Volcano, Vanuatu

Capturing the Acoustic Radiation Pattern of Strombolian Eruptions using Infrasound Sensors Aboard a Tethered Aerostat, Yasur Volcano, Vanuatu

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