HR: 1340h
AN: T23A-1207    [Abstracts]
TI: Shear wave Splitting beneath the East European Craton
AU: Wuestefeld, A
EM: andreas.wuestefeld@web.de
AF: Geoscience Montpellier, UMR 5243 - CC 60 Place E. Bataillon, Montpellier, 34095, France
AU: * Bokelmann, G
EM: Bokelmann@gm.univ-montp2.fr
AF: Geoscience Montpellier, UMR 5243 - CC 60 Place E. Bataillon, Montpellier, 34095, France
AB: The method of shear-wave splitting provides a unique possibility to identify seismic anisotropy and to measure orientations of fast and slow wave propagation directions. Seismic anisotropy results from the lattice-preferred orientations of anisotropic minerals. Though the depth of the anisotropic layer is less well-constrained there is evidence that most of the splitting occurs in the asthenosphere and/or lithosphere. Lithospheric anisotropy is often referred to as "frozen" anisotropy as it renders past tectonic events. On the other hand, asthenospheric anisotropy results from the deformation associated with plate motion. That deformation aligns the minerals, in particular olivine, in the direction of relative motion. Previous investigations in central Europe indicate fast directions aligning along the craton margins. This might perhaps indicate asthenospheric flow around the thick lithospheric keel, but other causes such as fossil anisotropy can not be excluded for that region to the west of the East European Craton. We investigate the continuation of this shear wave splitting pattern further to the East, using 18 broadband stations located on the East European Craton. Several arguments support the presence of lithospheric anisotropy under the craton: 1) large-scale coherence within each of the 4 constituing blocks but significant variations between the blocks; 2) a lacking correlation with absolute plate motion vectors; 3) reasonable correlation between fast axes orientations with magnetic anomaly alignments, the latter reflecting only crustal features. The good correlation between these crustal features with the mantle-induced shear-wave splitting strongly supports the idea of vertically coherent deformation throughout the upper mantle and crust. The observed splitting orientations reflect thus the last tectonic events of each block, frozen-in into the lithosphere.
DE: 1518 Magnetic fabrics and anisotropy
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8103 Continental cratons
SC: Tectonophysics [T]
MN: 2007 Fall Meeting