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Structure et tectonique du prisme d'accrétion de Nankai dans la zone Tokai par imagerie sismique en trois dimensions

Abstract : The Nankai margin in the Tokai area has not ruptured during the last seismic episode of 1944-1946, that affected the rest of the margin. A strong seism is therefore to be expected in this area in the next years. To better constrain the extend of the seismogenic zone, a 3D seismic survey was carried out in 2000 on the Nankai wedge. This PhD thesis lies in the double thematic aspects of this survey, both methodological and geological. The methodological aspect covers the consideration of 3D imaging specificities compared to classical 2D imaging. During the acquisition, the geometry of the source-receivers display has to be perfectly well known. Thanks to a new method developped ad hoc, the geometry has been reconstructed with an excellent precision. The processing also sensibly ameliorated the obtained images, even though some objects are not obvious in the data. 3D images however allowed to much better constrain the position of major faults (Tokai, Kodaiba) in depth, and then to better understand the wedge kinematics. The geological aspect revealed that the deformation of the margin is dominated by Quaternary events, that affected the cover of the forearc basin that was previoulsy very quiet. Several folding phases can be distinguished, amongst which one in the front of the basin, that can be chronologicaly linked to the subduction of an oceanic ridge. The study of the BSR also indirectly allowed to give an order of magnitude of erosionnal and depositionnal proccesses on the margin. Large observed landslides can be simply linked to seismic activity of the margin, without any pore fluids overpressure. Finally, a subducting volcano was observed and is possibly the cause for the Tokai fault inactivation, that does not present any sign of recent activity. of recent activity.
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https://tel.archives-ouvertes.fr/tel-00008139
Contributor : Victor Martin <>
Submitted on : Thursday, January 20, 2005 - 11:53:36 AM
Last modification on : Thursday, October 29, 2020 - 3:01:18 PM
Long-term archiving on: : Friday, April 2, 2010 - 9:45:06 PM

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  • HAL Id : tel-00008139, version 1

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Victor Martin. Structure et tectonique du prisme d'accrétion de Nankai dans la zone Tokai par imagerie sismique en trois dimensions. Géophysique [physics.geo-ph]. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00008139⟩

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