Feasibility of three-dimensional density tomography using dozens of muon radiographies and filtered back projection for volcanos

Nagahara, Shogo; Miyamoto, Seigo

doi:10.5194/gi-7-307-2018

Cited by 14 publications

(14 citation statements)

References 21 publications

(28 reference statements)

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“…The images revealed increased average rock densities across the east side of the activated Minamidake and underneath the deactivated Showa crater with a spatial resolution of ∼60 m. Despite the underestimated average densities due to the detection of energetic background muons, it is reasonable for us to interpret that the excessive density found in the current muographic image was produced by the formation of a volcanic plug. Multidirectional muography (Nagahara & Miyamoto, ) and its combination with high‐resolution gravity (Rosas‐Carbajal et al, ) are good candidates to achieve three‐dimensional monitoring of magma movements inside active volcanoes in the future.…”

Section: Discussionmentioning

confidence: 99%

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Plug Formation Imaged Beneath the Active Craters of Sakurajima Volcano With Muography

Oláh

Tanaka

Ohminato

et al. 2019

Geophysical Research Letters

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Sakurajima Muography Observatory captured the formation of a volcanic plug beneath the Showa crater with a spatial resolution of ∼60 m in accordance with the end of the eruption episode of Showa crater and the reactivation of Minamidake crater. The increase of average density was observed with above 3 σ standard deviation for both above the floor of Minamidake crater and beneath the floor of Showa crater, respectively, being interpreted as volcanic ejecta deposition and the formation of a volcanic plug laterally extended within a few hundreds of meters.

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Section: Discussionmentioning

confidence: 99%

“…Multidirectional muography (Nagahara & Miyamoto, 2018) and its combination with high-resolution gravity (Rosas-Carbajal et al, 2017) are good candidates to achieve three-dimensional monitoring of magma movements inside active volcanoes in the future.…”

Section: 1029/2019gl084784mentioning

confidence: 99%

Plug Formation Imaged Beneath the Active Craters of Sakurajima Volcano With Muography

Oláh

Tanaka

Ohminato

et al. 2019

Geophysical Research Letters

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“…A simulation study showed that at least 16 2D muon radiographic images captured from independent directions are necessary to reconstruct a 3D density model of a target with a reasonable resolution. 23) However, it is not practical to evenly distribute many muon detectors around a volcano having a rugged topography. Because long-term electric power supply is not feasible for such conditions, there is no alternative but to use the emulsion plates as muon detectors.…”

Section: Nonuniqueness Of Gravimetric Inversion For Subsurface Densitymentioning

confidence: 99%

“…Although the conduit is no longer blocked, Eqs. [19]- [23] still provide an appropriate model for computing the deformation and gravity changes during the eruption by considering negative values of "P and "V to model the deflating magma chamber. This formulation will be used to analyze the gravity change for a deflating pressure source in section 4.5.…”

Section: ½19mentioning

confidence: 99%

Advances in gravity analyses for studying volcanoes and earthquakes

Okubo

2020

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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This report highlights the usefulness and applicability of various gravimetric methods for studying earthquakes and volcanic activities. A high-resolution gravity anomaly map of Japan reveals areas with very steep horizontal gradients, where potential seismic faults are likely to be buried. Such traditional geoprospecting is coupled with novel cosmic-ray radiography to produce a fine-resolution (<100 m) three-dimensional density structure of a volcano. On the other hand, temporal gravity changes provide invaluable information about the process of earthquake faulting, volcanic eruptions, caldera formation, etc. Specifically, in this report we present our previous work on gravity research for solid earth science: (1) the first detection of coseismic gravity changes, (2) the virtual visualization of the rising and falling of magma in a conduit of Asama volcano, and (3) the large-scale lateral movement of magma during the Miyake-jima eruption in 2000.

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“…Muon tomography, consisting of combining muographies from several viewpoints, allows the reconstruction the 3-D density distribution. To conduct a muon tomography, Nagahara & Miyamoto (2018) used the method of filtered back projection, which has the advantage of not relying on any a priori information. They show that the method requires data from at least a dozen of viewpoints to allow a proper 3-D reconstruction, which is for now impractical.…”

Section: Introductionmentioning

confidence: 99%

Bayesian joint muographic and gravimetric inversion applied to volcanoes

Barnoud

Cayol

Niess

et al. 2019

Geophysical Journal International

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SUMMARY Gravimetry is a technique widely used to image the structure of the Earth. However, inversions are ill-posed and the imaging power of the technique rapidly decreases with depth. To overcome this limitation, muography, a new imaging technique relying on high energy atmospheric muons, has recently been developed. Because muography only provides integrated densities above the detector from a limited number of observation points, inversions are also ill-posed. Previous studies have shown that joint muographic and gravimetric inversions better reconstruct the 3-D density structure of volcanic edifices than independent density inversions. These studies address the ill-posedness of the joint problem by regularizing the solution with respect to a prior density model. However, the obtained solutions depend on some hyperparameters, which are either determined relative to a single test case or rely on ad-hoc parameters. This can lead to inaccurate retrieved models, sometimes associated with artefacts linked to the muon data acquisition. In this study, we use a synthetic example based on the Puy de Dôme volcano to determine a robust method to obtain the resulting model closest to the synthetic model and devoid of acquisition artefacts. We choose a Bayesian approach to include an a priori density model and a smoothing by a Gaussian spatial correlation function relying on two hyperparameters: an a priori density standard deviation and an isotropic spatial correlation length. This approach has the advantage to provide a posteriori standard deviations on the resulting densities. Using our synthetic volcano, we investigate the most reliable criterion to determine the hyperparameters. Our results suggest that k-fold Cross-Validation Sum of Squares and the Leave One Out methods are more robust criteria than the classically used L-curves. The determined hyperparameters allow to overcome the artefacts linked to the data acquisition geometry, even when only a limited number of muon telescopes is available. We also illustrate the behaviour of the inversion in case of offsets in the a priori density or in the data and show that they lead to recognizable structures that help identify them.

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Feasibility of three-dimensional density tomography using dozens of muon radiographies and filtered back projection for volcanos

Cited by 14 publications

References 21 publications

Plug Formation Imaged Beneath the Active Craters of Sakurajima Volcano With Muography

Plug Formation Imaged Beneath the Active Craters of Sakurajima Volcano With Muography

Advances in gravity analyses for studying volcanoes and earthquakes

Bayesian joint muographic and gravimetric inversion applied to volcanoes

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