## 4 Results and Discussion
This pattern of anomalies is related to the post-mining character of the test site, i.e., the presence of depressions filled with anthropogenic formations of lower density than the surrounding  
Figure 7: Gravimetric map: (**a**) Gravimetric anomalies in the Bouguer reduction; (**b**) Residual anomalies. Moicene forms. In the test site located in the SE part of test field three (E), the distribution of residual anomalies shows an extensive, relatively negative anomaly running from SW to NE. The lowest value of \(-0.05\) mGal is located in the southern part of this site. The image of residual anomalies, as in the case of the previous test site, reflects the post-mining nature of the area, where, next to higher bulk density tertiary deposits, there are lighter anthropogenic formations. The last test site (F) shows the same character. The 2D and 3D gravimetric modeling methods made it possible to quantify the image of the rock mass in the light of gravimetric data. The Bouguer anomaly maps confirmed the glaciotectonic character of the geological structure, emphasized the geostructural forms, and helped to define the extent of possible land deformations. The areas exposed to the threat of surface deformations are related to the consolidation of the ground disturbed by mining. In gravimetric images, these are associated with the occurrence of negative anomalies, and result from a shortage of mass. The process of tightening the goals (underground workings) loosens the sediments above, and thus reduces their density in relation to the intact surroundings. These sites were further investigated with the Electrical Resistivity Tomography surveys. The results, in the form of eight apparent resistivity cross-sections beneath the ERT geophysical profiles, and their geophysical interpretation, indicate three distinct lithological complexes, spatially differing in resistivity and physical-mechanical properties (Table 1). The delineation of boundaries between individual complexes is based only on the values of the physical parameter, which is the resistivity of the geological medium. Their spatial extent, in an exemplary profile corresponding to the profile line marked in Figure 5, is shown in Figure 8.  
Based on the adopted criteria, a schematic diagram of the hydrogeological cross-section, with marked extent of deformation zones caused by the exploitation or weathering of brown coal seams (Figure 9), was constructed. The discontinuity zones of poorly permeable and impermeable grounds constitute potential channels for the migration of non-cohesive formations into mining excavations zones. Based on the analysis of these results \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Complex** & **Range of Resistivity [\(\Omega\)m]** & **Filtration Coefficient [m/s]** & **Lithological Classification** \\ \hline \multirow{2}{*}{loam} & \multirow{2}{*}{\(<\)40} & Impermeable to poorly & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } \\  & & permeable (1 \(\times\)\(10^{-8}\) –\(1\times\)\(10^{-6}\)) & \\ \hline \multirow{2}{*}{sand-loam} & \multirow{2}{*}{40–200} & poorly permeable to permeable & \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } \\  & & & non-cohesive formations (sands, dusty \\ \hline \multirow{2}{*}{sand} & \multirow{2}{*}{\(>\)200} & Permeability (1 \(\times\)\(10^{-4}\)–\(1\times\)\(10^{-3}\)) & \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } \\  & & anthropogenic formations. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Lithological and physic-mechanical classification of resistance complexes in the study area. Figure 8: Exemplary geoelectrical profile with geophysical interpretation. in ERT profiles, a map of subsidence risk areas was interpreted, and further geophysical studies provided additional geological information and identified locations of potential ground disturbance of anthropogenic (mining) origin (Figure 10).