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Theses

Diffusion multiple des ondes sismiques et expériences analogiques en ultrasons

Abstract : This thesis manuscript is devoted to the study of the seismic and ultrasonic wave propagation in complex media. Two methods are proposed to take advantage of the phase information contained in diffuse waves. Several applications are discussed. 1) Weak localization of seismic waves is observed on a volcano (Auvergne). This field experiment demonstrates the presence of multiple scattering in coda waves, and allows the direct measurement of the transport mean free path of the sub-surface that quantifies the heterogeneities. 2) A passive imaging technique is proposed: it is based on the correlation of diffuse field or noise, a correlation that yield the elastic or acoustic Green function between passive sensors as if one of them was a source. This technique is generalized to open scattering media. A physical interpretation based on a Time-Reversal analogy is developed. The time symmetry of the correlations is studied, with means of numerical simulations, seismic experiment in Alaska, and ultrasonic experiment in the lab using a small medium analogous to the Earth's crust. The role of scattering and source position is emphasized. 3) The passive imaging technique is used to perform the tomography of a layered medium, to image of interfaces and localized reflectors. In the end this technique is applied to Lunar seismic noise records, acquired by four geophones emplaced on the Moon during Apollo 17 mission (1972). This last observation demonstrates the feasibility of correlating the noise to image the subsurface on other planets than the Earth, which should provide a novel avenue for future extraterrestrial exploration missions.
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https://tel.archives-ouvertes.fr/tel-00010020
Contributor : Eric Larose <>
Submitted on : Thursday, September 1, 2005 - 1:38:00 PM
Last modification on : Thursday, November 19, 2020 - 3:54:28 PM
Long-term archiving on: : Friday, April 2, 2010 - 10:01:46 PM

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  • HAL Id : tel-00010020, version 1

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Éric Larose. Diffusion multiple des ondes sismiques et expériences analogiques en ultrasons. Sciences de la Terre. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00010020⟩

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