Our investigation is carried out under the framework of the project INFLUINS (Integrated Fluid
Dynamics in Sedimentary Basins), which is devoted to studies of relationship between the near-
surface and deeper fluids and material flows. The project links geology, hydrogeology, mineralogy,
geophysics, basin analysis, remote sensing and other geoscience topics. A geophysical investigation is
necessary in order to explain the internal structure of the Thuringian Basin, and to develop a joint 3D
model of its underground using seismic, gravimetric, magnetic and borehole measurements. In our
study we use mainly gravity and magnetic data. A detailed structural model forms an essential
boundary condition for models of fluid transport, one of the central goals of the project INFLUINS.
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Corresponding author. Tel.: +49 3641 948751; fax: +49 3641 948662. E-mail address: Ilya.Prutkin@gmx.de
Our new method for the 3D potential field data inversion has been tested on a local and isolated
gravity anomaly by Prutkin et al. (2011). For this anomaly, we primarily focused on a wide variety of
admissible solutions, which generate the same field. By interpreting the gravity and magnetic
anomalies for the Thuringian Basin, we deal with a larger geographic area. Both, the gravity and
magnetic data are inverted, taking into consideration the fact that they represent a complex
composition of various signals. In our study, we try to consider all available geological information to
obtain a unique solution.
First, we separate the sources into the deep, intermediate and shallow components by applying
successively the upward and downward continuation procedures. All components are inverted
separately. Here we deal for the first time with a problem of low frequencies, meaning that deep
masses generate long wavelengths, but the converse implication is not necessarily true. Here we
demonstrate how this problem can be solved by using additional geological information.
For intermediate wavelengths, we begin with the three largest negative gravity anomalies, which are
correlated with the negative magnetic anomalies. From each anomaly, we remove a model of the
regional field. We then approximate the resulting residual anomaly by the field of several 3D line
segments and subtract their effects. The residual field is inverted for 3D topography of a contact
surface. We apply our inversion algorithms to transform segments into three restricted bodies, which
are interpreted geologically as granitic intrusions. Finally, we combine all objects and obtain a 3D
model of the main intermediate sources.
Among shallow sources, there are two main gravity anomalies, which are correlated with the
magnetic ones. We transform magnetic data to so-called pseudo-gravity and compare it with
measured gravity. Their high spatial correlation indicates that both, the gravity and magnetic
anomalies are likely related to the same source. We then invert the anomalies for the 3D topography
of density interface, which is interpreted as an uplift of the crystalline basement. For several local
areas, we invert negative gravity anomalies for the geometry of salt deposits. This interpretation is
supported by drilling data from existing boreholes.
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