A long-term monitoring of micro-tectonic movements in caves at Cape Kaliakra, Northeast Bulgaria: Correlation with seismic events and precipitation

This article aims to present the results of an 11-year monitoring of micro-tectonic movements along dangerous cracks opening in caves at Cape Kaliakra, Northeast Bulgaria. Two 3D monitoring devices TM71, were installed in two caves, the purpose of which is to monitor the movements of the rock blocks along dangerous cracks. The obtained results of microdisplacement measurements from 2013 to 2023 show active movement along the observed cracks. This is expressed not only in linear trends but also in sudden shifts and short-term shifts followed by recovery (oscillations). The comparison with the local and regional seismicity shows a correlation between the abrupt movements and seismic events along the Batovo fault. Data from the automatic weather station in the town of Kavarna point to a possible link between some oscillation type movements and heavy rainfall in the research area. The results of the analyzes show the importance of long-term monitoring in clarifying the recent geodynamics in the research area. The results obtained provide valuable information about the dynamics of this region, and hence about the geomorphological evolution and the physical-geological hazardous phenomena. The registered movements show the connection between gravitational movements and tectonic ones. For the first time, data obtained through instrumental observations are published, proving the activity of fault structures in this part of Bulgaria. The results can also be used to predict dangerous slope destabilizations, as well as to reduce the risk of their occurrence.