DEEP ELECTROMAGNETIC SOUNDING IN TURKMENIA

This paper presents the results of interpretation of magnetotelluric and magnetovariational observations in a vast region, including the southern part of the Turanian plate and the South Caspian megadepression. Both 1-D and 2-D interpretations fail to explain the main peculiarities of the natural magnetotelluric and magnetovariational fields observed in the region. The 3-D interpretation used in the paper is based on thin-sheet modelling and inversion algorithms developed by the authors. The final model consists of an inhomogeneous surface layer and a conductive layer, embedded in the otherwise laterally uniform medium in the crust under the Kopet-Dagh mountains. The surface layer conductance varies between 100 S and 13 000 S, and the crustal anomaly has a conductance of about 2500 S. The layered regional structure includes a conductive layer at a depth of 80-100km, whose conductance is about 1800 S. The model explains all of the main features of the observed magnetotelluric and magnetovariational fields in the region.