- 1Applied Near-Surface Geophysics and Remote Sensing Group, Institute for Earth System Science and Remote Sensing, University of Leipzig, Leipzig, Germany
- 2State Office for Geology and Mining Saxony-Anhalt, Germany
- 3ScaDS.AI (Center for Scalable Data Analytics and Artificial Intelligence), University of Leipzig, Leipzig, Germany
The Mansfelder Mulde (German for trough) around Lutherstadt Eisleben is considered as an active subsidence area. Deep-seated subrosion is the potential reason for large- and small-scale earth surface deformation. The appearance of sinkholes as potentially hazardous surface expression of karst has led to increasing interest in the area. Specifically, in the study area Neckendorf in the southwest of the Mansfelder Mulde, two major sinkholes occurred in the early 2000s, affecting a federal road and an allotment garden site. At the end of 2021, surface cracks formed again along a main road just 800 meters away from the previous sinkholes. This process is attributed to ongoing subsidence in the adjacent field. The continuous ground movement, coupled with significant surface cracking along an additional road causing severe traffic problems, necessitated the complete closure of both roads in December 2022.
The subsidence area has been investigated by the State Office for Geology and Mining (LAGB) Saxony-Anhalt since 2022 and is since March 2024 a research topic of the UL. During first field measurements, the edge areas of the subsidence were surveyed using Electrical Resistivity Tomography (ERT). In addition, three seismic stations were recently (November 2024) installed to investigate the ground movements in the context of the large-scale subsidence. Currently, no results from the seismic data are available. Once the field data has been retrieved, it will be analyzed in conjunction with the existing ERT data to discuss the subsidence event. With the help of long-distance (deep) ERT we aim to decipher the hydrogeologic conditions of the Anhydrite and Gypsum Zechstein layers, at the supposed base of the subrosion. One objective was to detect, cracks and loosening zones also in the overlying lower Buntsandstein layers. Several profiles were created along the neighbouring fields and the affected roads. Due to different electrical material properties compared to the surrounding soil material, the suspected subrosion features appear as anomalies. ERT showed a clear difference between farmed and abandoned, non-farmed areas. Higher resistivities indicate a deformed subsoil, and with high probability an extension of the loosening zones beyond the crack formation visible on the surface. Near vertical lower-resistance structures could indicate water-saturated fracture zones in context of the main subsidence. Furthermore, the effects of a defective water pipe were possibly detected with ERT. As it is currently not possible to estimate how the subsidence will develop, the evaluation of geophysical data is significant for local hazard assessment and should, above all, provide the affected farmers with clarity about the subsoil situation of their fields and inform local stakeholders about the ongoing process.
How to cite: Silbermann, M., Khosravichenar, A., Aalijahan, M., Ginga, M., Rappsilber, I., Sänger, N., Gauert, C., Seidemann, J., Umlauft, J., and Al-Halbouni, D.: Geoelectrical and seismic investigation of a subsidence geohazard zone in Neckendorf, Saxony-Anhalt, Germany , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20756, https://doi.org/10.5194/egusphere-egu25-20756, 2025.
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