Structural setting of the Čertovka landslide (Ústí nad Labem, Czech Republic): morphostructural analysis and electrical resistivity tomography

Abstract

The Certovka landslide at Vaňov south of Usti nad Labem, Czech Republic, is developed in a steep slope of the Labe River Valley (LRV). A major episode of landsliding occurred in the first months of 1995, and the slope at Vaňov has been subjected to geological and geomorphological investigation since then. This paper presents structural setting of the Certovka landslide based on the latest geological survey, detailed geomorphological mapping, morphostructural analysis and results of electrical resistivity tomography. The landslide was found to be initiated at the boundary between Late Eocene to Oligocene basaltic lavas above and volcaniclastics below, with bedding dipping against the slope (anaclinal slope). The underlying volcaniclastics show tendency to argillization and have a much lower rock strength, which acts as an important factor of slope instability at the site. The Certovka landslide is a complex slope deformation consisting of several landslides and flowslides, with boulder streams merging into a boulder accumulation further downslope. The headscarp area of the landslide developed at one of the structural levels built by basaltic lavas and forming step-like morphology of the valley slope. The headscarp coincides with the course of a regional E–W-striking Vaňov Fault which underwent multiple tectonic history and is associated with a dense fracture system including smooth slickensides on the headscarp. Structural observations combined with detailed knowledge of the anatomy of the landslide based on airborne data, surface data and geophysical data permitted to conclude on structural controls of landsliding and predict future evolution of the slope deformation. Future landsliding will be initiated at structural levels of basaltic rocks, with the headscarps developed along fractures parallel to the Vaňov Fault. The probable gradual retreat of headscarps at the individual structural levels along the slope profile denotes a retrogressive landslide style.