Joint use of multi-temporal satellite interferometric and geotechnical data for monitoring and investigating the kinematics of an urbanized relict landslide

The residual kinematics of relict landslides involving built areas can represent a severe source of risk. Such slope movements can be monitored through ground-based geotechnical and remote sensing techniques, like interferometric synthetic aperture radar (InSAR). In this study, to investigate the residual slow movements of a relict landslide affecting the Mendatica village (Liguria, NW Italy), a coupled analysis of multi-temporal displacement monitoring datasets from slope inclinometers and InSAR (ERS, RADARSAT, ENVISAT, COSMO-SkyMed and Sentinel-1) was performed. Owing to the favorable satellite acquisition geometry and a rather continuous temporal efficiency of in situ geotechnical equipment, the study emphasized the complementariness between the two techniques. The joint analysis allowed reconstructing the patterns of movement over almost 30 years. Furthermore, by exploiting the spatial correspondence and long temporal overlap of InSAR and geotechnical measurements, together with geomorphological evidence, the displacement components were combined to reconstruct the subsurface geometric structure and the kinematic model of the landslide. The results revealed that the residual landslide activity consists of composite movements involving major translational movements coupled with weak rotational mechanisms, mainly driven by erosion at the landslide toe. The study outcomes represent useful knowledge for the zonation of movement intensity for medium-to-long term landslide risk management strategies.