C/X-band SAR interferometry used to monitor slope instability in Daunia, Italy

Thanks to the all-weather, day-night capability to detect and quantify accurately small ground surface deformations, Synthetic Aperture Radar (SAR) Interferometry (InSAR) techniques are attractive for landslide hazard investigations. In particular, multi-temporal InSAR techniques allow to detect and monitor millimetric displacements occurring on selected point targets exhibiting coherent radar backscattering properties (mainly buildings and other man-made structures). In the present work we apply the SPINUA (Stable Point INterferometry over Un-urbanised Areas) multi-temporal processing technique [1] to the Daunia region located in Southern Apennines, Italy. This region includes several small hill-top towns affected by slope instability problems and is of particular interest for the Civil Protection – Regione Puglia Authority, which is one of the end users of the deformation maps derived by multi-temporal interferometric analysis of satellite data. This site was already investigated in the past though interferometric analysis [2] by using ERS-1/2 SAR data provided by ESA. In this work we present results obtained by processing SAR data acquired by the ENVISAT ESA satellite (, medium spatial resolution) as well as by the TerraSAR-X satellite (X-band high resolution) launched by DLR in 2007. Thanks to the finer spatial resolution with respect to data, X-band InSAR applications appear very promising for monitoring single man-made structures (buildings, bridges, railways and highways) as well as areas where data show low PS density. This is the case, in particular, of the Daunia region which is scarcely urbanised. Indeed, the results obtained with X-band data suggest that many more man-made and natural targets behave as persistent scatterers than in . Moreover, thanks again to the higher resolution, it should be possible to infer reliable estimates of the displacement rates with a number of SAR scenes significantly lower than in within the same time span or by using more images acquired in a narrower time span. Finally, with shorter wavelengths the sensitivity to LOS displacements is increased together with the capability of detecting very low displacements rates (as the pre- and post-failure movements related to landslides are expected to be). The displacements maps obtained by processing both C- and X-band SAR data will be presented for a selected number of towns affected by slope instability. Results will be commented with particular attention paid to the advantages provided by the new generation of X-band high resolution space-borne SAR sensors.