On the electrical crust-mantle structure in Fennoscandia: no Moho and the asthenosphere revealed?
An interpretation of the geomagnetic inductive response function,
C(o, 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 variancereduced
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 Fennoscandian
shield, beginning at a depth of between 155-185 km, and of 60 km
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.
Geophysical Journal of the Royal Astronomical Society, 68, 371-388, 1982.
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Alan G Jones / 8 October 2007 /