Integrated geophysical imaging of a mountain landslide – A case study from the Outer Carpathians, Poland

In the presented case study, the authors applied the multimethod approach utilising geophysical imaging with estimated uncertainty to the landslide in Cisiec, southwest Poland. Application of multiple geophysical methods such as electrical resistivity tomography (ERT), multichannel analysis of surface waves (MASW), refraction seismic method, ray-based seismic tomography, and reflection imaging was aimed at obtaining a detailed and high-resolution image of the subsurface. Drone-based digital terrain models (DTM) supported the subsurface imaging by providing a detailed view of the landslide surface. Accurate GPS-based geodesy conducted during data gathering was used to complete information about the topography of the area and correlate the results of geophysical surveys. The combination and transfer of information between methods allow solving multiple reflection imaging problems, especially lack of borehole information. The final result presents the detailed geophysical images of the landslide with a recognized depth of main slip surface ranging from 16 to 36 m. Because the study site is used as a ski slope, detailed information about the landslide structure is needed to provide safety for nearby construction. The methodology proposed in this paper can be used in similar case studies, where fast and cost-effective recognition of a landslide is required.