HR: 1340h
AN: T13A-0447    [Abstracts]
TI: Shear Wave Splitting on the East European Platform
AU: * Wuestefeld, A
EM: wueste@dstu.univ-montp2.fr
AF: Universite Montpellier II, Laboratoire de Tectonophysique, Place Eugene Bataillon, Montpellier, 34095 France
AU: Bokelmann, G H
EM: Goetz.Bokelmann@dstu.univ-montp2.fr
AF: Universite Montpellier II, Laboratoire de Tectonophysique, Place Eugene Bataillon, Montpellier, 34095 France
AU: Zaroli, C
T13A-0447 AF: Ecole de Physique du Globe de Strasbourg, 5, rue René Descartes, Strassbourg, 67084 France
AU: Barruol, G
EM: barruol@upf.pf
AF: Université de la Polynésie française, Faaa Aéroport Tahiti, Faaa, Ta BP 6570 French Polynesia
AB: The method of shear wave splitting (e.g. Silver & Chan, 1991; Savage, 1999) provides a unique possibility to identify seismic anisotropy in seismological observations, i.e. to measure the orientation of fast and slow wave propagation directions. These directions result from the lattice-preferred orientation 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. Anisotropy occurring in the upper portions of the lithosphere is often referred to as 'frozen' anisotropy as it displays old tectonic events. On the other hand, asthenospheric anisotropy results from deformation associated with plate motion. This deformation aligns the minerals (in particular olivine) in the direction of relative motion. Here we study seismic anisotropy under 17 broad band stations of the East European Platform (EEP) that is roughly located between Poland and the Ural Mountains, the Black Sea and Arctic Ocean. Some stations operate for more than a decade and thus provide an ideal dataset with a wide range of backazimuths of events. Those stations may therefore allow a study of mantle anisotropy with a resolution beyond a single anisotropic layer. This region is particular due to the presence of a thick lithosphere which reaches deep into the mantle and thus represents a mechanical obstacle to motion of the (Eurasian-) plate relative to the mantle. This mechanical obstacle might also channel the mantle flow as has been suggested for the American Plates. First results as well as previous studies in central Europe indicate fast directions aligning with the margins of the EEP. Though plate motion is slow (~ 20mm/a; Gripp & Gordon, 2002) the motion vector of the European plate correlates well with this study. There is a clear change of fast direction at the western edge of the craton. The data were processed using a novel "SplitLab" workflow, based on the Matlab platform. This graphical user interface provides the entire shear wave splitting process from seismogram request of data centers to the splitting measurements, as well as the post-processing of the results.
DE: 8103 Continental cratons
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 9335 Europe
SC: Tectonophysics [T]
MN: Fall Meeting 2005