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Déformation active d'une région intraplaque à déformation lente :Le cas de la France. Sismicité et modélisations thermomécaniques 2D et 3D

Abstract : An unresolved problem in seismology concerns the occurrence of unexpectedly strong earthquakes within intraplate slow deforming regions. This paradox (strong magnitude, small deformation) has been the subject of numbers of studies in areas such as the Eastern United States and Canada (Talwani 1988, Assameur et Mareschal, 1995, Pollitz et al., 1999). Following these works, this thesis presents a study in France and in particular in central and western France where we dispose of valuable seismicity catalogues, good geological knowledge and recent geophysical results. In a first step, we revised the seismotectonics of Normandy, Brittany, Charente region and the Massif Central by relocating the earthquakes, computing new focal mechanisms and defining the short scale stress field variation, by inversion of focal mechanisms. This re-evaluation was made possible by the increase of permanent seismological stations. We evidence a regionally significant NW trending sigma 1 strike-slip regime overprinted by local extensional perturbations in three distinct areas. These perturbations are located in the south of Brittany, between the Armorican Massif and the Massif Central (Poitou) and in the eastern Massif Central. The scale of the perturbations suggests that these processes are of crustal or lithospherical scale. We propose to associate the extensive perturbations of southern Brittany and Poitou to the influence of a southward traction force initiated in the Bay of Biscay and the perturbation of eastern Massif Central to surrection at the apex of an ascending mantle plume located at the base of the lithosphere. The study of faults distribution, heat flow and Euler solutions, computed from the regional Bouguer anomaly, helps to better understand the earthquakes distribution, stress concentration and the occurrence of earthquakes of magnitude higher than 4 in a very slowly deforming area. Then, these hypothesis are studied by 2D and 3D thermomechanical modeling, taking into account structural, thermal and rheological parameters.
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https://tel.archives-ouvertes.fr/tel-00010156
Contributor : Yves Mazabraud <>
Submitted on : Thursday, September 15, 2005 - 9:06:42 AM
Last modification on : Monday, December 14, 2020 - 9:48:34 AM
Long-term archiving on: : Friday, September 14, 2012 - 2:25:26 PM

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  • HAL Id : tel-00010156, version 1

Citation

Yves Mazabraud. Déformation active d'une région intraplaque à déformation lente :Le cas de la France. Sismicité et modélisations thermomécaniques 2D et 3D. Géologie appliquée. Université Nice Sophia Antipolis, 2004. Français. ⟨tel-00010156⟩

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