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Are the crustal and mantle conductive zones isotropic or anisotropic?

100%

Berdichevsky M. , Pushkarev P.

Acta Geophysica

2006

tom Vol. 54, no. 4

333-342

One of the significant problems of modern deep magnetotellurics is the recognition of anisotropy in the crustal and mantle conductive zones. In the paper we perform numerical experiment comparing several 2D models of crustal and mantle isotropic and anisotropic prismatic conductors. Anisotropy is modeled by alternat-ing horizontal or vertical thin layers of different resistivities (the vertical layers are parallel to the prism strike). Using these models, we examine conditions under which the magnetotelluric and magnetovariational response functions distinguish between isotropy and anisotropy. The resolution of MT and MV studies depends on the sediments conductance, lithosphere resistance and deep conductor width. Calcu-lations show that the most favorable conditions for anisotropy studies are observed in the active regions characterized by small sediments conductance (10-20 S) and moderate lithosphere resistance (108 Ohmźm2). However, in the stable regions, where sediments conductance exceeds 50-100 S and the lithosphere resistance comes up to 109 Ohmźm2, the crustal and mantle anisotropic and isotropic conduc-tors manifest themselves in the equivalent magnetotelluric and magnetovariational functions, which cannot distinguish between anisotropy and isotropy and admit both the interpretations.

Electrical structure of the upper mantle beneath Central Europe: results of the CEMES project

51%

Semenov V. , Jóźwiak W. , Pęk J. , Adam A. , Ladanivskyy B. , Logvinov I. , Pushkarev P. , Vozár J.

Acta Geophysica

2008

tom Vol. 56, no. 4

957-981

In the years 2001–2003, we accomplished the experimental phase of the project CEMES by collecting long-period magnetotelluric data at positions of eleven permanent geomagnetic observatories situated within few hundreds kilometers along the south-west margin of the East European Craton. Five teams were engaged in estimating independently the magnetotelluric responses by using different data processing procedures. The conductance distributions at the depths of the upper mantle have been derived individually beneath each observatory. By averaging the individual cross-sections, we have designed the final model of the geoelectrical structure of the upper mantle beneath the CEMES region. The results indicate systematic trends in the deep electrical structure of the two European tectonic plates and give evidence that the electrical structure of the upper mantle differs between the East European Craton and the Phanerozoic plate of west Europe, with a separating transition zone that generally coincides with the Trans-European Suture Zone.