For the first time, a systematic magnetotelluric survey has been made of the North German sedimentary basin. It was intended to obtain details concerning the thickness, extent and structure of the sedimentary basin. A model of the basin was derived from data collected at about 50 sites. The model contains the distribution of the integrated conductivity of the strata above and below the Zechstein base, and depth values for the magnetotelluric (MT) basement ranging from 9 km ( in the south) to 18 km (in the north). The integrated conductivity of the strata above the Zechstein base decreases from 4000 mho in the north to 5 mho in the south. In the pre-Zechstein this trend is reversed, with 8000 mho in the south decreasing to 2000 mho in the north. In the southern part unexpectedly low resistivities (approximately 1 ohm .m) occur in the pre-Zechsteiti. The model calculations suggest that the source of the North German conductivity anomaly lies in the upper crust. The anomaly is caused by the contact of poorly conducting material with very thick (approximately 10 km) well-conducting sediments, which additionally show lateral conductivity variations outside the contact area.
Iterative two-dimensional magnetotelluric calculations commonly converge very slowly, especially when applied to large grids. Consequently, the authors have used three methods of accelerating the convergence which supplement each other, and thereby make the iteration process about ten times faster.The influence of grid spacing on the accuracy of apparent resistivity curves varies.
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