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Croissance des failles normales et des rifts continentaux : développement du Golfe d'Aden et dynamique de la plaque Arabe

Abstract : The deformation of the eastern margin of the North Gulf of Aden are first studied in this thesis from data acquired during a field mission and campaign at Sea (Incense Sheba). The field data show that the faults are highly segmented and widely scattered directions (N60 ° E to N120 ° E to major faults). To understand these features, analog models were performed to better understand the mechanisms involved in the creation of these fault networks: the influence of levels ductile reactivation of inherited faults and boundary conditions responsible for the extension. The influence of viscous levels on the growth of normal fault networks is studied using analog and digital models. The presence of viscous levels and their resistance control the geometry of major faults. A low level of viscous resistance induces large faults farther apart, limiting blocks slightly deformed. The only small flaws that are initiated are then located near major faults and are widely scattered directions. To account for the geometry of fault system in the Gulf of Aden, it is necessary to take into account the obliquity of the direction of extension of the rift and fault networks inherited. Analogue models of oblique reactivation were performed. They are well aware of the geometries observed in the Gulf of Aden, as in other rifts like the Gulf of Suez rift Lake Tanganyika or the Viking Graben. Reactivation of these phenomena occur on the edges of the rift or late extension direction (N160 ° E) is recorded on the ground. To better define the boundary conditions leading to the formation of networks of faults observed on land and at sea, it is necessary to understand the mechanisms responsible for the formation of the Gulf of Aden. To do this, models of analog system lithosphere-upper mantle explore the role of the subduction of the Tethys in the north. The collision of Africa-Arabia comes at an early stage in the Northwest while subduction is still active in the east. In models, this phenomenon causes the intraplate deformation in North-Eastern Africa, whose geometry, in the presence of a weak representative of the Afar hot spot, is very similar to that of Afro-Arab rifts. In this configuration, an area of ​​oblique extension (similar to the Gulf of Aden) is generated, without weakness or preexisting lithospheric rifting propagation. This result implies a particular model of oblique rifting may explain the presence of N160 ° E extension, late on the edges of the rift, perpendicular to the rift that locates the direction of the Gulf today.
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Submitted on : Tuesday, May 3, 2011 - 2:45:23 PM
Last modification on : Thursday, December 10, 2020 - 10:54:50 AM
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  • HAL Id : tel-00590417, version 1


Nicolas Bellahsen. Croissance des failles normales et des rifts continentaux : développement du Golfe d'Aden et dynamique de la plaque Arabe. Sciences de la Terre. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00590417⟩



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