Integrated geophysical and geological surveys reveal new details of the large Montescaglioso (southern Italy) landslide of December 2013

Abstract

A methodological approach based on the integration of different survey techniques may be particularly suitable for the study of areas with complex geology such as those affected by landslide phenomena. The results obtained by the application of combined electrical resistivity tomography (ERT) technique, ambient seismic noise measurements (single station and array), geological investigation and granulometric analysis to characterize and study a landslide occurred on December 3rd, 2013 in Basilicata region (southern Italy) are presented and discussed. The landslide partially affected the peri-urban area of Montescaglioso town and caused damages to small-medium enterprises, infrastructures, and housing. The analysis of ambient noise signals made possible to estimate the depth of the contacts between the main geological formations outcropping in the area and revealed the existence of directional resonance effects. The discontinuities observed by the ERT have confirmed the presence of different lithotypes and allowed illuminating the sliding surface at a depth of about 40 m in agreement with the seismic results and boreholes data. The shallow discontinuities inferred from geophysical surveys were supported also by the results of a detailed granulometric analysis performed on a geognostic survey, confirming the presence of a heterogeneous sedimentary deposit in the area. In such complex context, the acquisition of spatially distributed geophysical properties permitted to increase the knowledge of the geological setting of the area, reaching a level of detail that cannot be observed by applying only a sparse discrete direct sampling. The integration of all the obtained information allowed the delineation of geophysical discontinuities related to the presence of sliding or weakness surfaces and areas with high water content that could contribute to future activation of the movement. This information was crucial to better understand the nature of the landslide, contributing to the planning and the implementation of risk mitigation actions and to the design of remediation works.