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The recently presented SqueeSARTM technique for SAR interferometry was applied to study the activity of 237 DSGSDs located in the Central European Alps. The analysis of displacement rates within each DSGSD suggests that 90 % of these instability phenomena are active. Considering the huge volume involved in these phenomena, we conclude that DSGSDs can significantly contribute to denudation of the Alpine orogen, by means of an extremely long-term slow displacement rate.

Ground deformation studies based on Differential GPS (DGPS) measurements and Permanent Scatterers InSAR (PSI)* analysis using ERS (1992-2000) and ENVISAT (2003-2010) radar data have been conducted on Zakynthos Island (Western Greece) covering the period 1992 to 2012. These results were compared, validated and integrated with geological, geotectonic and seismological data to evaluate possible pre-earthquake deformation process, and the present tectonic regime. The PSI results indicate that a slight subsidence had occurred during the period 1992-2000, while uplift has mainly observed in 2003-2010. DGPS results for 2005-2006 indicated strong opening of the southern part of the island, while in the period 2006-2012 the amplitude of deformation is relatively smaller. The occurrence of the seismic outbreak that took place offshore to the south of Zakynthos during 2005-2006 may have contributed to the different deformational pattern as revealed by the ERS and ENVISAT PSI products, and also elucidate the DGPS results.

Ground deformation studies based on Differential GPS (DGPS) measurements and Permanent Scatterers (PS) Interferometric analysis have been conducted in the seismically active area of the Cephallonia and Ithaca islands. DGPS measurements for the period 2001 to 2010 revealed horizontal component of deformation generally ranging from 3-8 mm/yr with the largest values at the western and southern parts of the island. Considering the vertical deformation, two periods are distinguished on the basis of DGPS and PS Interferometry: The first one (1992 to 2003) is consistent with anticipated motions associated with the main geological and tectonic features of the island. The second one (2003 to 2010) has been tentatively attributed to dilatancy in which relatively small uplift (2-4 mm/yr) occurred along the southern and southeastern parts of the island, while larger magnitudes (>4 mm/yr) took place at the western part of Cephallonia. These large magnitudes of uplift over an extended area (>50 km) are consistent with the hypothesis of dilatancy. On the basis of the analysis of 53 differential ASAR interferograms and the PS product, it has been derived that dilatancy effect should have commenced some time in mid-2005. If this interpretation is correct, it may foreshadow the occurrence of very strong earthquake(s) sometime in the near future.

During the last 8 years Permanent Scatterer interferometry (PSInSAR) has been widely used as a powerful tool for surface deformation monitoring both for scientific and commercial projects. A few years after the introduction of this technology, it was highlighted how the constraints on the stability of the radar signature of the targets used as opportunistic measurement points could be too tight. Forcing the PS to be coherent in all interferometric pairs used in the analysis could cause the loss of information coming from scatterers exhibiting PS behavior only in a subset of SAR images. Another concern was related to the estimation of the DEM reconstruction: the problem here is to take advantage of the PS framework trying to extend the set of image pixels where an estimation of the elevation is possible. Apart from geometrical decorrelation and variations of the Doppler centroid values of the acquisitions, temporal decorrelation phenomena strongly limit the coherence values of many scatterers within the area of interest. The question arising is whether the presence of radar scatterers exhibiting high or moderate coherence levels at low temporal baselines (typically one month) can be useful for real life applications and, in case of positive answer, which algorithms are most suited to extract useful information from slowly decorrelating scatterers. Although this topic is still the subject of extensive research activities, this paper summarizes some facts that, in the authors’ opinion, will be the base of any future algorithm. In particular, the analysis of the coherence matrix computed on a pixel-by-pixel basis is shown to be a key-element of any study of decorrelating targets. Its modeling can be extremely useful to extract feature parameters for image segmentation