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GPS network monitors the Western Alps' deformation over a five-year period: 1993–1998

Vigny, C. and Avouac, J.-P. (2002) GPS network monitors the Western Alps' deformation over a five-year period: 1993–1998. Journal of Geodesy, 76 (2). pp. 63-76. ISSN 0949-7714. doi:10.1007/s00190-001-0231-8.

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The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely unknown due to small relative motions and the insufficient accuracy of the triangulation data. As a consequence, several tectonic problems still remain to be solved, such as the amount of N–S convergence in the Occidental Alps, the repartition of the deformation between the Alpine tectonic units, and the relation between deformation and rotation across the Alpine arc. In order to address these problems, the GPS ALPES group, made up of French, Swiss and Italian research organizations, has achieved the first large-scale GPS surveys of the Western Alps. More than 60 sites were surveyed in 1993 and 1998 with a minimum observation of 3 days at each site. GPS data processing has been done by three independent teams using different software. The different solutions have horizontal repeatabilities (N–E) of 4–7 mm in 1993 and 2–3 mm in 1998 and compare at the 3–5-mm level in position and 2-mm/yr level in velocity. A comparison of 1993 and 1998 coordinates shows that residual velocities of the GPS marks are generally smaller than 2 mm/yr, precluding a detailed tectonic interpretation of the differential motions. However, these data seem to suggest that the N–S compression of the Western Alps is quite mild (less than 2 mm/yr) compared to the global convergence between the African and Eurasian plate (6 mm/yr). This implies that the shortening must be accomodated elsewhere by the deformation of the Maghrebids and/or by rotations of Mediterranean microplates. Also, E–W velocity components analysis supports the idea that E–W extension exists, as already suggested by recent structural and seismotectonic data interpretation.

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Avouac, J.-P.0000-0002-3060-8442
Additional Information:© 2002 Springer, Part of Springer Science+Business Media. Received: 27 November 200; accepted: 17 September 2001. We are grateful to everyone involved in the long-term collaboration on the GPS-ALPES project since 1991. Special thanks to all surveyors from many different French, Italian, and Swiss institutes. Special thanks to C. Sue, whose detailed review greatly helped in improving the paper. The bulk of this work has been achieved to a large part in the framework of the Tectoscope-Positionement program in 1993 and the GeoFrance-3D program in 1998, ans sponsored by the INSU-CNRS, BRGM, CEA/LDG, CERGA, CNES, EDF, ESGT, ETH (Zurich), IGN, ING (Roma), and IPSN.
Group:Seismological Laboratory
Funding AgencyGrant Number
Centre National d'Études Spatiales (CNES) (France)UNSPECIFIED
Subject Keywords:GPS; ALPES; Tectonics
Issue or Number:2
Record Number:CaltechAUTHORS:20120910-135500795
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33971
Deposited On:12 Sep 2012 18:55
Last Modified:09 Nov 2021 23:05

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