Seismic-wave anisotropy of the subcrustal lithosphere of Fennoscandia

Jaroslava Plomerova (1), Tellervo L. Hyvonen (2), Vladislav Babuska (1), Daniel Kouba (1) & Ludek Vecsey (1)

(1) Geophysical Institute, Academy of Science of the Czech Republic, Prague
(2) Institute of Seismology, University of Helsinki, Finland

Abstract

We have analysed P-wave travel-time delays and shear-wave splitting at permanent seismological stations of Fennoscandia to model seismic anisotropy of the mantle lithosphere. We also include results achieved recently from observations at two arrays of mobile stations in southern Sweden (Plomerova et al., 2001a,b). Joint inversion and/or interpretation of anisotropic parameters evaluated from body waves and modelled by olivine aggregates with hexagonal or orthorhombic symmetry, resulted in 3D self-consistent anisotropic inferences of the mantle lithosphere with plunging symmetry axes. Distinct lateral changes of orientation of the anisotropy, which occur at prominent tectonic boundaries, such as the Protogine zone in south-central Sweden or the Archean-Proterozoic boundary in eastern Fennoscandia, mark large domains of the mantle lithosphere. Different orientations of anisotropies at seismic stations situated within both the Archean and Proterozoic parts of eastern Fennoscandia indicate that each of these large tectonic units is most probably composed of several smaller lithospheric domains of different origin. Considering the crustal thickness, which ranges from 30 to about 65 km, and the lithosphere thickness about to 200-250 km, the remaining mantle lithosphere of about 150km is thick enough to accommodate the large-scale anisotropic observations.

Whole poster

Not available.

Svekalapko /Europrobe Workshop, Lammi, Finland, 2001.

References
[1] Plomerova, J., Arvidsson, R., Babuska, V., Granet, M., Kulhanek, O., Poupinet, G. and J. Sileny, An array study of lithospheric structure across the Protogine zone, Varmland, south-central Sweden - signs of a paleocontinental collision, Tectonophysics, Vol. 332, No. 1-2, pp. 1-21, 2001a.
[2] Plomerova, J., Babuska, V., Vecsey, L., Kouba, D. and TOR Working Group, Seismic anisotropy of the lithosphere around the Trans-European Suture Zone (TESZ) based on teleseismic body-wave data of the TOR experiment, Tectonophysics, in print, 2001b.