## 3 InSAR Adopted Tecnique  
The classical differential SAR Interferometry (InSAR) is a technique that allows us to estimate the ground surface movements occurred between two different passes of the satellite over the same area using Synthetic Aperture Radar (SAR) data. The phase difference at each pixel is calculated after proper image co-registration resulting in a new image, called interferogram, an interference pattern made up of fringes [69]. Each fringe represents a ground movement along the sensor line of sight (LOS) equal to \(\lambda/2\) (where \(\lambda\) is the adopted radar wavelength). Figure 2: The archaeological sites of the ancient Sybaris (see inset in Figure 1 for its location). There are many physical phenomena contributing to phase measurements: phase variations within a pixel, the contribution of orbital variations, topography, atmosphere, and displacement. These contributions are estimated and then removed so to obtain only the effective ground displacement. Our goal is to investigate the temporal evolution of the detected deformations. To this aim several different approaches have been proposed in the last decade to generate time series of ground displacement, capable of measuring the ground velocities rates with accuracies of \(\sim\)1 mm/yr [70]. In this work, we applied the Small Baseline Subset InSAR technique (SBAS; [20]). The used SAR images were coupled based on constraints of small temporal and spatial baselines. The SBAS algorithm combines these acquisitions, also included in different interferometric subsets, using a minimum norm criteria combination of the velocity deformation, based on the Singular Value Decomposition (SVD) method. During the SBAS processing the estimation and removal of temporally decorrelated atmospheric artefacts are performed using double-pass filtering in the temporal and spatial domains, as explained in [20]. Moreover, we used the SRTM DEM (90-m resolution) for the subtraction of topography phase ([[http://www2.jpl](http://www2.jpl)]([http://www2.jpl](http://www2.jpl)). nasa.gov/srtm). Once the displacement time series is retrieved, the mean ground velocity in the time period covered by the data was calculated. In detail, we applied the SBAS technique to four image datasets, two acquired from the European Space Agency (ESA) Envisat sensor and two from the Italian Space Agency (ASI) COSMO-SkyMed satellites. The first group contains 32 Envisat images acquired on the descending orbit (track 222, frame 2803), in the period 2004-2010 imposing 700 days as maximum temporal baseline and 350 meters for the maximum perpendicular one and considering 100 pairs. Instead, the ascending dataset (track 86, frame 789) is formed by 38 ASAR images acquired in the period 2003-2010 setting 900 days for the maximum temporal baseline and 350 meters for the maximum spatial one resulting in 135 interferograms. The second group (COSMO-SkyMed data) was composed of 28 images from the ascending orbit considering 180 days for the maximum temporal baseline and 700 meters as maximum spatial baseline resulting in 137 interferograms, spanning the interval 2011-2013 and 12 images from the descending orbit, acquired in the interval 2011-2012 setting 100 days for the temporal and 1000 meters for the spatial maximum baselines respectively forming 47 interferograms. We used the Sarscape software (Sarmap, CH) applying a looking factors equal to 20 and 4 for the azimuth and range direction, respectively for the ascending and descending Envisat processing obtaining a ground resolution of 80 meters and 11, 12 for the COSMO-SkyMed case with a final ground posting of 25 meters; later downgraded to 100 meters for the post-processing analysis. The initial performed multi-looking operation reduced the image radar noise (speckle) and increased the signal to noise ratio.