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On the electrical crust—mantle structure in Fennoscandia: no Moho, and the asthenosphere revealed? |
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| Authors: | Alan G Jones |
| Institution: | Institut für Geophysik der Westfälischen Wilhelms-Universität. Correnstrasse 24, D-4400 Münster, Federal Republic of Germany |
| Abstract: | Summary. An interpretation of the geomagnetic inductive response function, C (ω, 0), observed at Kiruna in northern Sweden, is herein undertaken. The bounds of acceptable solutions are initially discovered by a Monte-Carlo random search procedure, and the best-fitting solutions are examined by the application of linear theory to the problem. The data are shown to have a higher degree of internal consistency than that described by the estimated variances of each datum. A further Monte-Carlo inversion of the variance- reduced data set gives solutions with well defined model parameters. The two major features of the models are: (1) a small, or non-existent, electrical conductivity variation across the seismic Moho boundary, and (2) the unequivocal existence of an electrical asthenosphere, under the Fenno- scandian shield, beginning at a depth of between 155–185 km, and of 60km minimum thickness. Both of these observations have seismic counterparts. Finally, possible mantle temperature profiles are deduced which depend on the assumptions and laboratory data employed. |
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