Volume Flow Rate Estimation for Small Explosions at Mt. Etna, Italy, From Acoustic Waveform Inversion

Díaz‐Moreno, Alejandro; Iezzi, Alexandra M.; Lamb, Oliver D.; Fee, David; Kim, K.; Zuccarello, Luciano; Angelis, Silvio De

doi:10.1029/2019gl084598

Cited by 14 publications

(17 citation statements)

References 42 publications

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“…The methodology here proposed is, for the first time, taking in consideration the acoustic propagation in the conduit by considering the effect of the conduit on the acoustic propagation outside the vent. We suggest that when linear theory of sound is applied to acoustic waves generated in the conduit (Diaz‐Moreno et al, 2019; Fee, Izbekov et al, 2017; Iezzi et al, 2019; Johnson et al, 2018; Kim et al, 2015; Watson et al, 2019; Yokoo et al, 2019), the effect of the impedance contrast between the open‐end vent and the atmosphere cannot be neglected to properly assess the source parameters and/or propagation outside the explosive vent.…”

Section: Resultsmentioning

confidence: 99%

“…The reliability of the numerical model is tested by comparing the simulation result with the analytical solutions (Levine & Schwinger, 1948). Recent works developed a full‐waveform inversion technique, based on 3D numerical Green's functions computed by FDTD modeling to estimate volumetric flux rate from infrasound data (De Angelis et al, 2016; Diaz‐Moreno et al, 2019; Fee, Izbekov et al, 2017; Iezzi et al, 2019; Kim et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Modeling the Acoustic Flux Inside the Magmatic Conduit by 3D‐FDTD Simulation

Lacanna

Ripepe

2020

JGR Solid Earth

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Infrasound measurements at open-vent volcanoes are crucial parameters for monitoring and exploring the explosive source dynamics. Volcano infrasound depicts the pressure variation within the volcanic conduit generated by the sudden expansion of volcanic gases during the fragmentation process, and it can provide important constraints on the explosive source parameters (i.e., volumetric flux and exit velocity). The acoustic source of volcanic explosions is modeled by infrasonic signals measured near the volcano vent (<3 km) assuming linear theory of sound and considering the effects of topography and atmosphere on the acoustic wavefield. However, little is known on the initial conditions within the volcanic conduit. In linear acoustics, the wavefield in a cylindrical duct propagates as a plane wavefront, which becomes spherical outside the vent. The acoustic impedance at the open end of the duct is a function of the vent radius and the pressure wavelength, and it controls the acoustic wavefield radiated outside the duct in terms of amplitude and radiation pattern. We present here a 3D-Finite Difference Time Domain (FDTD) numerical method to evaluate the scattering effects on the infrasound signal produced by topography around the crater and along the source-receiver path in terms of Green's function. Once the effects of topography are removed, we show how pressure perturbation is largely affected by the impedance contrast at the vent which, when not considered, is introducing errors in the way we quantify explosive dynamics.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling the Acoustic Flux Inside the Magmatic Conduit by 3D‐FDTD Simulation

Lacanna

Ripepe

2020

JGR Solid Earth

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“…(2019), and Diaz‐Moreno et al. (2019) aimed to investigate the stability and significance of the dipole component for multipole inversions. Kim et al.…”

Section: Inversion Solution Investigationmentioning

confidence: 99%

“…Previous studies such as Kim et al (2012), Iezzi et al (2019), andDiaz-Moreno et al (2019) aimed to investigate the stability and significance of the dipole component for multipole inversions. Kim et al (2012) used consistent dipole solution azimuth as one metric to investigate the dipole solution, though they note that the dipole they find might be due to topography since they did not incorporate 3-D Green's functions for their propagation term.…”

Section: Multipole Solution: Azimuth Inclination and Rectilinearitymentioning

confidence: 99%

Synthetic Evaluation of Infrasonic Multipole Waveform Inversion

et al. 2022

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Acoustic source inversions estimate the mass flow rate of volcanic explosions or yield of chemical explosions and provide insight into potential source directionality. However, the limitations of applying these methods to complex sources and their ability to resolve a stable solution have not been investigated in detail. We perform synthetic infrasound waveform inversions that use 3‐D Green’s functions for a variety of idealized and realistic deployment scenarios using both a flat plane and Yasur volcano, Vanuatu as examples. We investigate the ability of various scenarios to retrieve the input source functions and relative amplitudes for monopole and multipole (monopole and dipole) inversions. Infrasound waveform inversions appear to be a robust method to quantify mass flow rates from simple sources (monopole) using deployments of infrasound sensors placed around a source, but care should be taken when analyzing and interpreting results from more complex acoustic sources (multipole) that have significant directional components. In the examples we consider the solution is stable for monopole inversions with a signal‐to‐noise ratio greater than five and the dipole component is small. For most scenarios investigated, the vertical dipole component of the multipole explosion source is poorly constrained and can impact the ability to recover the other source term components. Because multipole inversions are ill‐posed for many deployments, a low residual does not necessarily mean the proper source vector has been recovered. Synthetic studies can help investigate the limitations and place bounds on information that may be missing using monopole and multipole inversions for potentially directional sources.

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“…At the local scale, microphones are deployed either as individual sensors within distributed networks or as smallaperture arrays (i.e., tight clusters of three or more instruments at 50-150 m from one another) at distances of between few hundreds of meters to within 20 km of an active volcanic vent. Data from distributed networks have traditionally been used for absolute source location and event discrimination (e.g., Cannata et al, 2009), and to evaluate eruption source parameters (e.g., Caplan-Auerbach et al, 2010;Fee et al, 2017;De Angelis et al, 2019;Diaz-Moreno et al, 2019). On the other hand, the close spacing between sensors deployed as a smallaperture array allows detection of coherent infrasound even in low signal-to-noise ratio (SNR) conditions, characterization of the direction-of-arrival (DOA), and the apparent speed of propagation of acoustic waves.…”

Section: Introductionmentioning

confidence: 99%

Uncertainty in Detection of Volcanic Activity Using Infrasound Arrays: Examples From Mt. Etna, Italy

et al. 2020

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The injection of gas and pyroclastic material from volcanic vents into the atmosphere is a prolific source of acoustic waves. Infrasound arrays offer efficient, cost-effective, and near real-time solutions to track the rate and intensity of surface activity at volcanoes. Here, we present a simple framework for the analysis of acoustic array data, based on least-squares beamforming, that allows to evaluate the direction and speed of propagation of acoustic waves between source and array. The algorithms include a new and computationally efficient approach for quantitative assessment of the uncertainty on array measurements based on error propagation theory. We apply the algorithms to new data collected by two 6-element infrasound arrays deployed at Mt. Etna during the period July-August 2019. Our results demonstrate that the use of two infrasound arrays allowed detecting and tracking acoustic sources from multiple craters and active vents associated with degassing and ash-rich explosions, vigorous and frequent Strombolian activity, opening of new eruptive fractures and emplacement of lava flows. Finally, we discuss the potential use of metrics based on infrasound array analyses to inform eruption monitoring operations and early warning at volcanoes characterized by episodic intensification of activity.

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Volume Flow Rate Estimation for Small Explosions at Mt. Etna, Italy, From Acoustic Waveform Inversion

Cited by 14 publications

References 42 publications

Modeling the Acoustic Flux Inside the Magmatic Conduit by 3D‐FDTD Simulation

Modeling the Acoustic Flux Inside the Magmatic Conduit by 3D‐FDTD Simulation

Synthetic Evaluation of Infrasonic Multipole Waveform Inversion

Uncertainty in Detection of Volcanic Activity Using Infrasound Arrays: Examples From Mt. Etna, Italy

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