Detecting Landslide Activity by SAR Interferometry

Operational monitoring of slope instabilities by SAR Interferometry poses a number of challenges due to the limited spatial extent of the landslide areas and rainy conditions usually associated with mass movement events. In this work we present the results of the application of both conventional DInSAR techniques, and a point-by-point, multitemporal study of the long-term stability of selected high-coherence objects on the ground. The techniques were applied to selected test sites in the Central and Southern Apennines of Italy. Results obtained by processing a number of ERS SAR images acquired over the test areas before, during and after critical events are presented. The evaluation of the results is performed through the comparison with data from ground based techniques. The various factors influencing the suitability of the selected data for interferometric applications, i.e. resolution, temporal and spatial baselines, and times of acquisition, are assessed. For one of the test sites, an application of the so-called "permanent scatterers" (PS) technique, originally proposed by the POLIMI group, is being attempted to monitor small displacements between points exhibiting a high long-term phase coherence and a strong and stable backscatter level.