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Tomographie à l'aide de décalages temporels d'ondes sismiques P : développements méthodologiques et applications

Vadim Monteiller 1
1 Département des Sciences de la Terre et de l'Environnement
CISM - Centre Interdisciplinaire Scientifique de la Montagne
Abstract : Improving our understanding of crustal processes requires a better knowledge of the geometry and the position of geological bodies. In this study we have designed a method based upon double-difference relocation and tomography to image, as accurately as possible, a heterogeneous medium containing seismogenic objects. Our approach bas been not only to introduce double-difference in tomography, but rather to partly revisit tomographic schemes for chosing accurate and adapted numerical strategies. We used a finite-difference solution to the Eikonal equation (Podvin and Lecomte, 1991) for travel-time computation and a Tarantola-Valette approach for bath the double- difference and the 3D tomographic inversion to find accurate earthquake locations and seismic velocity estimates. Though an efficient estimation of the squared root of the inverse model covariance matrix in the case of the gaussian correlation function, we use correlation length and a priori model variance criteria to determine the optimal solution. Double-difference relocation of similar earthquakes is performed in the optimal velocity model, making absolute and relative locations less biased by the velocity model. Double difference tomography is achieved by using high-accuracy time delay measurements. These algorithms have been applied to earthquake data recorded in the vicinity of Kilauea and Mauna Loa volcanoes for imaging the volcanic structures. They allow to find stable and detailed velocity models : regional tomography allows to retrieve unambiguously the structure of Hawaii island, and double difference tomography shows a detailed image of the southern Kilauea Caldera -East Rift Zone region magmatic complex.
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https://tel.archives-ouvertes.fr/tel-00653731
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Submitted on : Tuesday, December 20, 2011 - 10:01:24 AM
Last modification on : Friday, November 6, 2020 - 3:29:57 AM
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  • HAL Id : tel-00653731, version 1

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Vadim Monteiller. Tomographie à l'aide de décalages temporels d'ondes sismiques P : développements méthodologiques et applications. Géophysique [physics.geo-ph]. Université de Savoie, 2005. Français. ⟨tel-00653731⟩

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