## 3 Materials and Methods  
### Input SAR Data  
A total of 579 Sentinel-1 SAR scenes were used for the analysis. These were acquired by the radar sensors operating in C-band (5.405 GHz central frequency \(f\), and 5.547 cm wavelength \(\lambda\)) onboard the two satellites Sentinel-1A (launched on 3 April 2014) and Sentinel-1B (launched on 25 April 2016), which are phased at 180\({}^{\circ}\) to each other along the same near polar, sun-synchronous orbit at ~693 km altitude [50].  
The data were acquired in right-looking mode over a 6 year-long period between October 2014 and October 2020, along ascending track T146 (296 scenes: 15 October 2014-13 October 2020, acquired at 18:48 local time) and descending track T51 (283 scenes: 21 October 2014-13 October 2020, at 06:55 local time). The spatial footprints of the two data stacks are shown in Figure 1a and, with zoomed view, in Figure 3. As per the mission observation scenario over Europe [9], until September 2016, the site revisit at the study area was of 12 days (for each geometry), while an improvement to 6 days was later achieved thanks to the addition of Sentinel-1B. This means that each data stack consists of an image every 12 days in the period October 2014-September 2016, and every 6 days in September  
Figure 2: Simplified geomorphology of the area between the city of Crotone and the Capo Colonna promontory (modified after [49]).  
2016-October 2020. The frequency distribution of the available scenes along both tracks is shown in the time-bar in Figure 3. All scenes acquired in the period October 2014-October 2020 were used for the analysis.  
The employed acquisition mode was the Interferometric Wide (IW) swath, which is based on the Terrain Observation with Progressive Scans (TOPS) ScanSAR mode [51]. The IW swath width was 250 km, and the incidence angle \(\theta\) of the line-of-sight (LOS) varied between 31\({}^{\circ}\) and 46\({}^{\circ}\) from the near to the far range (i.e., \(\sim\)39\({}^{\circ}\) at scene center). The pixel spacing was 2.3 m in slant range and 14.1 m azimuth, resulting in ground range and azimuth resolution of 5 m and 20 m (single-look), respectively.  
The IW scenes were accessed through the GEP as Level-1 Single Look Complex (SLC) data (Figure 3), consisting of focused SAR products in zero-Doppler slant-range geometry, georeferenced using satellite orbit and attitude data.  
While Sentinel-1 IW data were acquired with dual polarization (co-polarized VV and cross-polarized VH), for this study the VV imagery was selected to run the P-SBAS processing, with the aim to guarantee continuity with previous co-polarization InSAR studies over the same region (see Section 5.1.1). Future research on this area will also attempt the exploitation of the VH data, both for comparison and in combination with VV. While the use of the VH data alone provides lower performance in terms of candidates and final persistent targets identification due to the generally lower amplitude of cross-polarized imagery (e.g., [52]), their combined exploitation with VV data through optimization methods proved capable to enhance the performance (e.g., [52; 53]). This could be a way forward for future research specifically aiming to compare the InSAR processing performance and accuracy at different polarizations.