(1) Geophysical Institute, Academy
of Science of the Czech Republic, Prague
(2) Institute of Petrology and Struct.
Geology, Faculty of Science, Charles University, Prague
Thanks to a systematic preferred orientation of olivine crystals, the continental mantle lithosphere exhibits a large-scale seismic anisotropy as a ubiquitous property observable by both body- and surface-wave velocities. Orientations of olivine (a,c) foliations, derived from spatial variation of P-wave delay times and S-wave splitting, are systematic within large blocks which are separated by sutures cutting the entire lithosphere thickness. The Variscan foldbelt in central Europe is characterised by anisotropic structures dipping divergently relative to Saxothuringian-Moldanubian suture. The dipping anisotropies may represent remnants of successive paleosubductions of ancient oceanic lithosphere. The overall pattern of large-scale anisotropy is complicated by later deformations along boundaries of colliding blocks, as well as by a present-day flow in the asthenosphere.
Not available.