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Images of lithospheric heterogeneities in the Armorican segment of the Hercynian Range in France

Abstract : The Armorican Massif is located in western France. It is a part of the Hercynian Range formed in several phases of SE-NW compression from Devonian to Carboniferous time (ca. 400-300 Ma). The main tectonic features are the North and South Armorican shear zones with WNW-ESE strike. In the framework of the GéoFrance3D program, we have installed 35 seismological stations along two NS lines crossing the main Hercynian WNW-ESE fault systems. The data set collected during the experiment allows us to compute a 3D P-velocity model and to map S-wave seismic anisotropy at depth using teleseismic shear waves splitting measurements. The South Armorican shear zone (SASZ) is characterized by a strong (4-5%) velocity contrast and a fast shear wave azimuth parallel to its strike. The North Armorican shear zone (NASZ) does not show any significant lithospheric signature. The tomographic image and anisotropy results suggest that the Armorican lithosphere consists of the juxtaposition of distinct lithospheric blocks assembled in a subduction type process predating the Hercynian Orogeny.
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Submitted on : Saturday, March 12, 2022 - 5:41:37 PM
Last modification on : Thursday, June 2, 2022 - 2:48:17 PM

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S. Judenherc, M. Granet, J. -P. Brun, G. Poupinet, J. Plomerová, et al.. Images of lithospheric heterogeneities in the Armorican segment of the Hercynian Range in France. Tectonophysics, 2002, 358, pp.121-134. ⟨10.1016/S0040-1951(02)00420-1⟩. ⟨insu-03607064⟩

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