Investigations on the structural setting of a landslide-prone slope by means of three-dimensional electrical resistivity tomography

Abstract

Over the last decades, many investigation methods have been applied on deep-seated gravitational slope deformations (DSGSDs) to achieve a better understanding of the geometrical patterns of phenomena that often are related to fast and hazardous surface slope movements. An integrated analysis based on geological field observations and geophysical measurements was developed and tested in the Cinque Torri DSGSD area (Eastern Dolomites, Italy) to investigate the influence of the slope setting onto the dynamics of the rocky pinnacles group. These pinnacles, which lie at the top of a Mesozoic sedimentary sequence, have volumes ranging between 25,000 and 100,000 m3. This contribution presents the results of the electrical resistivity tomography along with detailed topographic surveys carried out in order to define the slope setting down to a depth of about 50–60 m below the surface. The geophysical investigations particularly address the location of the major faults and the lithological contact geometries. By inspecting the structural patterns of the slope which control the DSGSD, and thus the lateral spreading of rocky pinnacles at the top, the interaction between slope setting and instabilities can be inferred. Geophysical data clearly outline some tectonic-driven displacements along with the major contacts between the different lithological units. Based on these results, the structural model of the site is better defined leading to a new insight into the local stratigraphy for modeling purposes. This method can be exported to other landslide areas where the logistic difficulties and local complexities make borehole drillings ineffective at capturing the 3D slope structure and deformation features.