Locating a weak change using diffuse waves: Theoretical approach and inversion procedure

Rossetto, Vincent; Margerin, Ludovic; Planès, Thomas; Larose, Éric

doi:10.1063/1.3544503

Cited by 74 publications

(77 citation statements)

References 35 publications

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“…The result is divided, as required by the Bayes formula, by the probability of going from A to B in time t, the boundary conditions. This formula is valid for any transport function G d in multiple scattering media [7]. As diffusion is a Markov process, equality (3) follows from the Chapman-Kolmogorov relation [19] …”

Section: Average Local Time For Diffusionmentioning

confidence: 98%

“…Simple boundary conditions, where the method of images applies, have been extensively discussed in Ref. [7].…”

Section: Discussionmentioning

confidence: 99%

“…up as long as c∆σL(x, t) ≪ 1, where ∆σ is the change of scattering cross-section [7]. In these three situations, one obtains a linear relation such as Equation (1).…”

Section: Applications Of Local Time To Imagingmentioning

confidence: 99%

“…The coda wave interferometry technique (CWI) uses time stretches on the wave field records to measure small velocity changes [5]. The LOCADIFF technique uses the correlation losses and produces images of the changes of scattering cross-section, that is to say the structural changes [7,8]. The absorption variation (AV) has been described in Section II.…”

Section: Applications Of Local Time To Imagingmentioning

confidence: 99%

“…The name of coda wave interferometry (CWI) is often met to gather these approaches. It was recently shown that the maximum of correlation obtained in this way contains informations about the changes in the scattering properties of the medium [7]. The data extracted by correlation are used as input in inversion techniques to produce images.…”

Section: Introductionmentioning

confidence: 99%

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Local time in diffusive media and applications to imaging

Rossetto

2013

Phys. Rev. E

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Local time is the measure of how much time a random walk has visited a given position. In multiple scattering media, where waves are diffuse, local time measures the sensitivity of the waves to the local medium's properties. Local variations of absorption, velocity and scattering between two measurements yield variations in the wave field. These variations are proportionnal to the local time of the volume where the change happened and the amplitude of variation. The wave field variations are measured using correlations and can be used as input in a inversion algorithm to produce variation maps. The present article gives the expression of the local time in dimensions one, two and three and an expression of its fluctuations, in order to perform such inversions and estimate their accuracy.

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Section: Average Local Time For Diffusionmentioning

confidence: 98%

“…Simple boundary conditions, where the method of images applies, have been extensively discussed in Ref. [7].…”

Section: Discussionmentioning

confidence: 99%

“…up as long as c∆σL(x, t) ≪ 1, where ∆σ is the change of scattering cross-section [7]. In these three situations, one obtains a linear relation such as Equation (1).…”

Section: Applications Of Local Time To Imagingmentioning

confidence: 99%

Section: Applications Of Local Time To Imagingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Local time in diffusive media and applications to imaging

Rossetto

2013

Phys. Rev. E

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Imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise

et al. 2013

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[1] Forecasting the location of an eruption is of primary importance for risk management in volcanic regions. Locating the underground structural changes associated with a potential eruption is also a key issue to better understand the dynamics at work in a volcano. Using recent results in wave physics, we develop an imaging procedure that is based on the sensitivity of multiply scattered waves to weak changes in heterogeneous media. This procedure allows to locate changes in both mechanical and scattering properties of the studied medium. We study ambient seismic noise from 19 broadband stations at the active volcano Piton de la Fournaise on Reunion Island, recorded from June to December 2010. During this period, two volcanic eruptions occurred at two different locations. We calculate the noise cross correlations and study two types of changes in the coda: apparent velocity variations related to changes in the elastic properties of the medium; and, waveform decoherence associated with variations in the scattering, and thus the geological structures. We observe that the temporal variations of both of these parameters provide potential precursors of volcanic eruptions at Piton de la Fournaise. The locations determined from the preeruptive and coeruptive changes in both parameters are in good agreement with the actual eruptive activities. These data demonstrate that the coda of ambient noise correlations contains deterministic information on the locations of the eruptive processes in an active volcano. Our analysis offers an original and significant constraint for the localization of forthcoming volcanic eruptions.Citation: Obermann, A., T. Planès, E. Larose, and M. Campillo (2013), Imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise,

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Large tectonic earthquakes induce sharp temporary decreases in seismic velocity in Volcán de Colima, Mexico

2014

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We used the ambient noise cross-correlation and stretching methods to calculate variations in seismic velocities in the region of Volcán de Colima, Mexico. More than 15 years of continuous records were processed, producing long time series of velocity variations related to volcanic activity, meteorological effects, and earthquakes. Velocity variations associated with eruptive activity are tenuous, which probably reflects the open state of the volcano during the study period. Fifteen events among 26 regional tectonic earthquakes produced sharp, temporary decreases in seismic velocities, which then recovered progressively following a linear trend as a function of the logarithm of time. For the 15 events, the amplitude of the perturbation increased almost linearly with the logarithm of the amplitude of the seismic waves that shook the edifice. The most dramatic apparent velocity variation was a drop of up to 2.6% during the nearby M7.4 Tecomán earthquake in 2003. In order to locate the perturbation in the horizontal plane we applied an inverse method based on the radiative transfer approximation. We also used an original approach based on the frequency dependence of velocity variations to estimate the depth of the perturbation. Our results show that the velocity variation was well localized in the shallow layers (< 800 m) of the volcano, with almost no variations occurring outside the edifice. We discuss several possible interpretations and conclude that the most plausible explanation for the velocity decreases is the nonlinear elastic behavior of the granular volcanic material and its mechanical softening induced by transient strains.

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Locating a weak change using diffuse waves: Theoretical approach and inversion procedure

Cited by 74 publications

References 35 publications

Local time in diffusive media and applications to imaging

Local time in diffusive media and applications to imaging

Imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise

Large tectonic earthquakes induce sharp temporary decreases in seismic velocity in Volcán de Colima, Mexico

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