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Active strike-slip faulting in the Chablais area (NW Alps) from earthquake focal mechanisms and relative locations

Delacou, Bastien ; Deichmann, Nicholas ; Sue, Christian ; Thouvenot, François ; Champagnac, Jean-Daniel ; Burkhard, Martin

In: Eclogae Geologicae Helvetiae, 2005, vol. 98, no. 2, p. 189-199

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    Titre
    • Active strike-slip faulting in the Chablais area (NW Alps) from earthquake focal mechanisms and relative locations
    Auteur
    • Delacou, Bastien. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP-2, CH-2007, Neuchâtel, Switzerland
    • Deichmann, Nicholas. Swiss Seismological Service, ETH-Zûrich, CH-8093, Zürich, Switzerland
    • Sue, Christian. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP-2, CH-2007, Neuchâtel, Switzerland
    • Thouvenot, François. Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Maison des Géosciences, CNRS/UJF, Campus Universitaire, 1381 rue de la Piscine, BP 53, FR-38041, Grenoble Cedex 1, France
    • Champagnac, Jean-Daniel. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP-2, CH-2007, Neuchâtel, Switzerland
    • Burkhard, Martin. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP-2, CH-2007, Neuchâtel, Switzerland
    Type de document
    • Postprint
    Langue
    • Inglese
    Publié dans
    • Eclogae Geologicae Helvetiae, 2005, vol. 98, no. 2, p. 189-199. Birkhäuser-Verlag; www.birkhauser.ch
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:317195
    Summary
    Abstract.: The Chablais area is characterized by a complex geological setting, resulting from the transport of nappes of various internal origins (the Prealpine nappes), thrusted in Oligocene times onto the Helvetic cover of the external zones of the Alps. While the structural setting and timing of nappe emplacement are well understood, current tectonics and associated faulting remain unclear. The detailed analysis of the Bonnevaux and Samoëns earthquakes, presented in this study, constitutes a significant contribution to the active tectonics of the Chablais area. The associated seismotectonic regime appears to be constant with depth, both focal mechanisms yielding a strike-slip regime, one in the crystalline basement at around 17km depth and the other probably cross-cutting the cover/basement interface at around 5km depth. Relative location techniques, applied in this study to the seismic sequence associated to the Samoëns earthquake, represents the best way to identify active faults in a region where neotectonic evidence is scarce and controversial. The resulting seismic alignment corresponds to the E-W oriented nodal plane inferred from the Samoëns main shock focal mechanism, thus defining an active near vertical E-W dextral fault. This strike-slip regime, compared to the current regional stress field, corresponds to the one observed in the Jura/Molasse basin area but contrasts with the exclusively dextral and NE-SW-oriented transcurrent regime of the Wildhorn/Martigny region