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Present-day deformation of the Pyrenees revealed by GPS surveying and earthquake focal mechanisms until 2011
Auteur(s) : Rigo, A. Vernant, Philippe Feigl, K. L. Goula, X. Khazaradze, G. Talaya, J. Morel, L. Nicolas, Jean-Marie
Auteurs secondaires : Institut de recherche en astrophysique et planétologie (IRAP) ; Université Paul Sabatier - Toulouse 3 (UPS) - Observatoire Midi-Pyrénées (OMP) - Centre National de la Recherche Scientifique (CNRS) Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Risques ; Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) - Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) University of Wisconsin-Madison [Madison] Institut Cartogràfic i Geològic de Catalunya (ICGC), Barcelona Universitat de Barcelona (UB) Laboratoire de Géodésie et de Géomatique (L2G ESGT CNAM) ; École Supérieure des Géomètres et Topographes (ESGT CNAM) ; Conservatoire National des Arts et Métiers [CNAM] (CNAM) - Conservatoire National des Arts et Métiers [CNAM] (CNAM) - Conservatoire National des Arts et Métiers [CNAM] (CNAM) Institut de Radioprotection et de Sûreté Nucléaire (IRSN)

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy P - Oxford Open Option A Oxford University Press (OUP)
Résumé : International audience
The Pyrenean mountain range is a slowly deforming belt with continuous and moderate seismic activity. To quantify its deformation field, we present the velocity field estimated from a GPS survey of the Pyrenees spanning 18 yr. The PotSis and ResPyr networks, including a total of 85 GPS sites, were installed and first measured in 1992 and 1995–1997, respectively, and remeasured in 2008 and 2010. We obtain a deformation field with velocities less than 1 mm yr−1 across the range. The estimated velocities for individual stations do not differ significantly from zero with 95 per cent confidence. Even so, we estimate a maximum extensional horizontal strain rate of 2.0 ± 1.7 nanostrain per year in a N–S direction in the western part of the range. We do not interpret the vertical displacements due to their large uncertainties. In order to compare the horizontal strain rates with the seismic activity, we analyse a set of 194 focal mechanisms using three methods: (i) the ‘r’ factor relating their P and T axes, (ii) the stress tensors obtained by fault slip inversion and (iii) the strain-rate tensors. Stress and strain-rate tensors are estimated for: (i) the whole data set, (ii) the eastern and western parts of the range separately, and (iii) eight zones, which are defined based on the seismicity and the tectonic patterns of the Pyrenees. Each of these analyses reveals a lateral variation of the deformation style from compression and extension in the east to extension and strike-slip in the west of the range. Although the horizontal components of the strain-rate tensors estimated from the seismic data are slightly smaller in magnitude than those computed from the GPS velocity field, they are consistent within the 2σ uncertainties. Furthermore, the orientations of their principal axes agree with the mapped active faults.
ISSN: 0956-540X

hal-01171752
https://hal.archives-ouvertes.fr/hal-01171752
DOI : 10.1093/gji/ggv052

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