Implications d'un saut de rift et du fonctionnement d'une zone transformante sur les déformations du Nord de l'Islande. Approches structurale, sismotectonique et radiochronologique

• Main Author: Garcia, Sebastian
• Other Authors: Laboratoire de tectonique (LT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris VI, Angelier Jacques
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2003
• Subjects: Islande; saut de rift; faille transformante; faille Husavik-Flatey; paleo-rift; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics; Mid-Atlantic Ridge; Kolbeinsey; Kolbeinsey Ridge; Tjörnes; Husavik; Húsavík; Iceland; Flatey
• Online Access: https://theses.hal.science/tel-00009796; https://theses.hal.science/tel-00009796/document; https://theses.hal.science/tel-00009796/file/tel-00009796.pdf

In Northern Iceland, the active rift is located 120 km eastward with respect to the Kolbeinsey Mid-Atlantic Ridge. The Tjörnes Fracture Zone connects these two rifts and accommodates a dextral transform motion. A major active fault of the Tjörnes Fracture Zone is the WNW-ESE trending Húsavík-Flatey Fault (HFF). The seismic activity associated to the HFF defined a nearly vertical fault surface that cuts through the 12 km thick seismogenic crust. Analyses of major structures combined with inversion of fault slip data allow us to discuss the kinematics and mechanics of the HFF since the Late Tertiary. For the present-day kinematics, we also use inversion of earthquake focal mechanisms provided by the Icelandic Meteorological Office. The main state of stress along the HFF corresponds to a dextral transtension, with an ENE-WSW trending extension due to the obliquity of the transform fault relative to the E-W direction of plate divergence. This overall mechanism is subject to slip partitioning that include an extension trending NW-SE, parallel to the HFF, and an extension trending NE-SW, perpendicular to the fault. These three regimes do not reflect a succession in time of tectonic events, but occur simultaneously at different places and in various chronological orders. They are thought to express the geometric accommodation of the transform motion in the oblique transform zone. Near the connection of the HFF to the Kolbeinsey Ridge, most dextral transform faults that trend parallel to the HFF are replaced by normal faults with a dextral component. On the opposite side of the HFF, at its junction with the northern Icelandic rift, two main transform fault segments have been mapped out. The northern fault directly connects to the northern Icelandic rift as a triple point junction, whereas the southern one progressively evolves from a WNW-ESE trending dextral transform fault to a N-S trending normal fault, parallel to the direction of the rift structures. One hypothesis, which would explain these structural differences, ...