Abstract
A multidisciplinary geophysical survey, consisting of electrical resistivity tomography (ERT), ground penetrating radar (GPR), shallow seismic refraction (SSR) and gravity survey (GS), was used to investigate the counter-slope scarps, one of the typical manifestations of the relaxed zones of rock massifs, and the possible initial stages of deep-seated landslides (DSLs). Two upper parts of the extensive DSLs within the Moravskoslezské Beskydy Mountains (Outer Western Carpathians - OWC) built by the sedimentary flysch rock were chosen as the testing sites.
A combined geophysical survey on the flysch rocks was performed on both localities to enhance our present findings. The survey revealed that the ERT is able to reliably detect underground discontinuities, which are man- ifested at the ground surface by one of the typical landforms (tension cracks, trenches, pseudokarst sinkholes, double-crested ridges and counter-slope scarps).
Previous studies suggested that bedrock discontinuities should be depicted by high-resistivity features within ERT surveying. According to SSR and GS, expected zones of weak- ened rock massif were not confirmed directly underneath the superficial landforms, but they were shifted.
Based on the SSR and GS measurements, the depicted high-contrast transitions between high- and low-resistivity do- mains within the ERT profiles were newly identified as possible manifestation of bedrock discontinuities. The re- sults of GPR measurements give only limited information on the sedimentary flysch rocks, due to shallow penetrating depth and locally strong signal attenuation.
The combined results of multidisciplinary geophysical surveying confirmed an importance of employing more than one geophysical technique for integrated interpre- tations of measured data. Integrated interpretations of the measured geophysical data provided a new insight into massif disintegration and the geomorphic origin of the landforms related to the DSL.