Use of differential SAR interferometry in monitoring and modelling large slope instability at Maratea (Basilicata, Italy)

Differential Synthetic Aperture Radar (SAR) interferometry (DiffSAR) allows, in principle, to measure very small movements of the ground and to cover in continuity large areas, so that it can be considered as a potentially ideal tool to investigate landslides and other slope instability. In this paper, we explore the use of this technique to improve our knowledge of the slope instability of a well-investigated area (the Maratea Valley), affected by continuous slow movements, producing an impressive “Sackung”-type phenomenon, which poses several unanswered questions. In particular, by using this technique, we analyse the time evolution of ground movements from 1997 to 2000. The slope movements during this same time interval have also been monitored in the past by using other techniques, such as electronic distance-meter (EDM) and GPS measurements: GPS and DiffSAR results are here compared. In our implementation of the DiffSAR technique, the problem of decorrelation noise is faced by using a phase unwrapping approach that allows to process sparse data, and the impact of atmospheric artefacts is reduced by performing a temporal analysis of the deformations observed in successive interferograms. In this study, we also show that it is possible to perform a temporal analysis of continuous slow landslide movements by using a limited number of ERS SAR data sets and low-precision topographic information. All the acquired data (EDM, GPS and DiffSAR) are consistent and allow a kinematic model of instability within the investigated time interval to be proposed. A map of slopes subject to different velocities of vertical displacements was delineated, modifying previous knowledge. Within the valley, progressive and almost linear displacements over time were confirmed.