THE PRESENT STATE-OF-ART OF LONG-PERIOD MAGNETOTELLURICS IN THE WESTERN PART OF THE BOHEMIAN MASSIF

Research into the complex geological structure of the Middle European Variscides in the western part of the Bohemian Massif has largely inte nsified in connection with the KTB deep borehole project in the Oberpf alz, Germany. First results of long period magnetotelluric studies alo ng an about 100 km long profile in SW Bohemia, close to the KTB drilli ng site, are presented here. They represent a partial step within a br oader project of constructing a 3-D geoelectrical model of the western margin of the Bohemian Massif and resolving the relations of anomalou s geoelectrical features to the geological structures of the region. T he data roughly fit a composite model of a 2-D regional structure, str iking E-W, overlaid by a layer of highly distorting near-surface inhom ogeneities. The distorting layer displays large anisotropy with prefer red conductivity in NW-SE to NNW-SSE direction. Attempt is made to est imate the absolute static shift of the MT curves. Several variants of 2-D models for the deep regional structure are discussed, including an anisotropic model which can qualitatively explain the discrepancy of the principal directions indicated by the MT and GDS data. The relatio n of the results obtained along the particular profile to the regional geoelectrical background is studied.