Three-dimensional electromagnetic modeling of the Trans-European Suture Zone (EMTESZ 3-D)
Zusammenfassung der Projektergebnisse
During the initial phase of the joint German-Polish-Russian research program "Electromagnetic Study of the Trans-European Suture Zone (EMTESZ)" a large number of long-period magnetotelluric (MT) sites were established in NW Poland and NE Germany with an extension in southernmost Sweden. The aim was to investigate the electrical resistivity structure in the broader area of the TESZ and the Northeast German-Polish Basin. Two-dimensional (2-D) inversion was carried out along the major profiles traversing the suture zone and the basin but it was clear from the beginning that the data were influenced by three-dimensional (3-D) local and regional effects. This was particularly evident on the Polish side where large salt diapirs complicate the electrical image while the profiles on the German side could rather safely be considered as 2-D. The recent availability of free 3-D inversion algorithms opened a new possibility in order to achieve a more unbiased image of the subsoil. For this purpose, additional measurements in the Polish Basin were carried out to obtain a more regional array structure suitable for 3-D inversion. The inversion runs were time and memory consuming and were calculated as part of a PhD work by Katarzyna Slezak on a Linux cluster at the Polish Academy of Sciences and on a Windows PC cluster at Free University of Berlin. Only the central parts of the study area could be included into the inversion due to memory and run-time considerations. The resulting preferred model shows a large conductor several hundred meters beneath the surface which is interpreted as the saline aquifer which is seen all over the Central European Basin. This conductor with an integrated conductivity of several thousand Siemens proved to be a major obstacle for assessing deeper structures in terms of resolution and depth extent. Therefore, a vast number of sensitivity calculations were done in order to exclude artifacts and to study the resolution of deeper structures. Nevertheless, a very prominent, elongated conductor could be resolved at several kilometers depth which is likely associated with the Variscan Front (VF). This major fault zone is thus seen as a lineament with significantly higher porosity for fluid content and/or might at least be partially graphitized. The VF can be traced in both the Polish and the Northeast German part of the Basin.
Projektbezogene Publikationen (Auswahl)
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3-D inversion of MT data to image the Variscan and Caledonian Deformation Fronts in NW Poland. 22nd Workshop on Electromagnetic Induction in the Earth, Weimar, Germany, 2014
Ślęzak, K., Jóźwiak, W., Nowożyński, K., Hoffmann, N., and Brasse, H.
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(2016): 3-D inversion of MT data for imaging deformation fronts in NW Poland, Pure Appl. Geophys.
Ślęzak, K., Jóźwiak, W., Nowożyński, K., and Brasse, H.
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Comparison of the 3-D inversion results with different type of MT data and model parametrizations, 23rd Workshop on Electromagnetic Induction in the Earth, Chiang Mai, Thailand, 2016
Ślęzak, K., Jóźwiak, W., Nowożyński, K., and Brasse, H.
