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Does Long-Term GPS in the Western Alps Finally Confirm Earthquake Mechanisms?

A. Walpersdorf 1, * L. Pinget 1 P. Vernant 2 C. Sue 3 A. Deprez 1 Stéphane Baize 4 Pascale Bascou 1 Sandrine Baudin 2 Olivier Bock 5 Pierre Briole 6 José Cali 7 Jean-Paul Cardagliaguet 8 Cédric Champollion 2 Olivier Charade 9 Jean Chéry 2 Nathalie Cotte 1 Olivier Dauteuil 10 Erik Doerflinger 2 Thierry Duquesnoy 11 Stéphane Durand 7 Romain Fages 11 Gilbert Ferhat 12 Mireille Flouzat 13 Bruno Garayt 11 Michel Gay 14, 15 Médéric Gravelle 16 Mikaël Guichard 16 Jacques Hinderer 12 François Jouanne 1 Charly Lallemand 13 Frédéric Masson 12 Elise-Rachel Mathis 11 Stéphane Mazzotti 2 Jean-Luc Menut 17 Frédérique Moreau 10 Laurent Morel 7 Joelle Nicolas 7 Jean-Mathieu Nocquet 17 Laurent Ott 14, 15 Félix Perosanz 18 Thierry Person 11 Etienne Poirier 16 Alexis Rigo 6 Lucie Rolland 17 Alvaro Santamaria-Gomez 18 Sébastien Saur 11 Oona Scotti 4 Anne Socquet 1 Patrice Ulrich 12 Joël van Baelen 19 Mathilde Vergnolle 17 Maurin Vidal 17 Christophe Vigny 6 Thierry Villemin 20 Guy Wöppelmann 16
Abstract : The availability of GPS survey data spanning 22 years, along with several independent velocity solutions including up to 16 years of permanent GPS data, presents a unique opportunity to search for persistent (and thus reliable) deformation patterns in the Western Alps, which in turn allow a reinterpretation of the active tectonics of this region. While GPS velocities are still too uncertain to be interpreted on an individual basis, the analysis of range-perpendicular GPS velocity profiles clearly highlights zones of extension in the center of the belt (15.3 to 3.1 nanostrain/year from north to south), with shortening in the forelands. The contrasting geodetic deformation pattern is coherent with earthquake focal mechanisms and related strain/stress patterns over the entire Western Alps. The GPS results finally provide a reliable and robust quantification of the regional strain rates. The observed vertical motions of 2.0 to 0.5 mm/year of uplift from north to south in the core of the Western Alps is interpreted to result from buoyancy forces related to postglacial rebound, erosional unloading, and/or viscosity anomalies in the crustal and lithospheric root. Spatial decorrelation between vertical and horizontal (seismicity related) deformation calls for a combination of processes to explain the complex present-day dynamics of the Western Alps.
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A. Walpersdorf, L. Pinget, P. Vernant, C. Sue, A. Deprez, et al.. Does Long-Term GPS in the Western Alps Finally Confirm Earthquake Mechanisms?. Tectonics, American Geophysical Union (AGU), 2018, 37 (10), pp.3721-3737. ⟨10.1029/2018TC005054⟩. ⟨hal-01947724⟩



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