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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS013 Oral Presentation 2225 European mantle lithosphere as a mosaic of plates with their own preassembly anisotropy signature Dr. Vladislav Babuska Seismology Geophysical Institute, Czech Acad. Sci. IASPEI Jaroslava Plomerova The concept of mobile terranes, or micro-continents, is considered as one of the most important additions to plate tectonics. However, we have only vague ideas about a role of large volumes of the mantle lithosphere in the formation of paleo-continents, in their brake-up and in later assemblage of their pieces into a new continent. Knowledge of seismic anisotropy is key to our understanding of tectonic fabrics in the deep lithosphere and sublithospheric mantle. To study building elements of the European continent, we have modelled three-dimensional seismic anisotropy of the mantle lithosphere from anisotropic parameters of teleseismic body waves. We invert and interpret jointly shear-wave splitting parameters and P residual spheres based on data from dense networks of temporary and permanent stations in several European regions. Changes in orientation of the large-scale anisotropy, caused by systematic preferred orientation of olivine, identify boundaries of domains of mantle lithosphere. Individual domains are characterized by a consistent large-scale orientation of anisotropy approximated by hexagonal or orthorhombic symmetry with generally inclined symmetry axes. The domains are separated by mapped tectonic boundaries (sutures), which cut the entire lithosphere. Such boundaries play important role in the lithosphere architecture and its dynamics, e.g. in the location of intraplate earthquakes and volcanic fields. Besides the change of anisotropy orientation at domain boundaries, we often observe a change of the lithosphere and/or crust thicknesses. We do not detect any fabric of the mantle lithosphere, which could have been produced by a collision of microcontinents in a volume detectable by large-scale seismic anisotropy. The observations of consistent anisotropy within individual blocks of the mantle lithosphere reflect frozen-in olivine preferred orientation, most probably formed prior to the assembly of microcontinents that created the modern European landmass. Therefore, our findings support a plate-tectonic view of the continental lithosphere as a mosaic of rigid blocks of the mantle lithosphere with complicated but relatively sharp contact zones. These contacts are blurred by the easily deformed overlying crust terranes. Keywords: european mantle lithosphere, fossil seismic anisotropy, mosaic of microplates

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS013 Oral Presentation 2226 High resolution mapping of the lithospheric thickness with S receiver functions Prof. Rainer Kind Seismology GFZ Potsdam IASPEI X. Yuan, F. Sodoudi, B. Heuer, W. Geissler, P. Kumar The lithosphere is a mechanical definition, not a seismic one (in contrast to the crust-mantle boundary). Seismic low velocity zones have been discovered in the upper mantle (mainly with surface waves), which are associated with the asthenosphere. The boundary between lithosphere and asthenosphere (LAB) was considered a gradual transition zone. The still relatively seismic new technique of S receiver functions is able to resolve the LAB with much higher resolution than previously possible. This technique can be applied to seismic data of the many existing permanent stations and to data from temporarely deployed stations. We have used S receiver functions in Greece, central Europe, Iceland and Greenland for mapping the LAB. Bebeath the northern Aegean we observe the African LAB at more than 200 km depth, in Germany and northern Bohemia it is near 80 km, whereas in southern Bohemia its depth reaches more than 100 km. The cratonic lithosphere east of the Trans European Suture Zone and in Greenland reaches 100-120 km. In Iceland we observe a clear negativ discontinuity at about 80 km depth. If this is the LAB, it would be in contrast to the postglacial rebound data. We expect to have a global LAB map in the near future using this new body wave technique. Keywords: lithosphericthickness, sreceiverfunctions, labmaps

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