## 2 Materials and Methods
### InSAR Analysis
#### 2.2.2 Method and Techniques  
With the aim of confirming the results obtained, two different types of software were used for the interferometric processing (Figure 3): the ESA SeNtinel's Application Platform (SNAP), which is a freely distributed under GNU General Public License, and the ENVI SARscape (L3 Harris Geospatial, Boulder, CO, USA), which is commercial software. SNAP was developed and is supported by ESA, offering an efficient, public tool for raster satellite data processing in optical and radar modes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Number of Pair** & **Satellite** &
\begin{tabular}{c} **Sub Swath** \\ **Number** \\ \end{tabular} & **Sensing Day** & **Pass Direction** \\ \hline
1 st (master) & Sentinel-1A & IW1 & 06 October 2020 & Ascending \\
1 st (slave) & Sentinel-1A & IW1 & 30 October 2020 & Ascending \\
2 nd (master) & Sentinel-1A & IW2 & 24 October 2020 & Desending \\
2 nd (slave) & Sentinel-1A & IW2 & 05 November 2020 & Desending \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Information on the Sentinel-1 SAR SCL images used. Figure 2: Age (**a**) and educational level (**b**) distributions of the responders to our questionnaire regarding the environmental effects induced by the 30 October 2020, Mw = 7.0, earthquake on Samos Island. In both formed interferometric pairs, the pre-seismic image was selected as the master image and the post-seismic as the slave. The preprocessing phase included splitting each sub swath with the selected bursts to cover the area under study and orbit refinement using the precise orbit files. In the second phase, we focused on the estimation of a constant azimuth offset for the whole sub swath using an enhanced spectral diversity method. Then, a constant range offset of the image using incoherent cross-correlation was estimated. The latter method exploits the overlapped areas of the adjacent bursts. The offset estimation in the azimuth and range directions was saved in a metadata file. This step practically is the co-registration of the master and slave images using the orbits and the 3 second Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM). In the next step, the interferogram and the coherence between the master and the slave images are saved in the same way as the master image. The phase of the sub swath is the same as the master image. slave images for each interferometric pair were computed. The last step of the main phase concerns debursting, because there is overlapping information in every burst with its neighboring ones, both in the range and azimuth directions. This is achieved by merging the bursts in the azimuth direction and preserving the phase information as well, while for the overlapping in the range direction, merging is done between the sub swaths. The next phase of the main processing starts with the topographic phase estimation and removal from the interferogram using the SRTM 3s DEM; then, in order to increase the noise-to-signal ratio, a power spectrum Goldstein filter [19] and a multi-looking operation were applied to reduce the speckle and obtain square pixels. The two wrapped interferograms, in ascending and descending geometry (Figure 4), are of good quality and contain the phase difference between the master and slave images due to the main seismic event. Limited areas of low coherence (temporal and spatial decorrelation) are locally presented in the interferograms (the decorrelation is more visible in the ascending interferogram) (Figure 4), because Sentinel-1 exhibits a high temporal resolution and a small orbital \"tube\" [20]. Moreover, in the ascending interferogram there is a topographically induced phase, especially in the central part of the island (Figure 4). Relatively small aftershocks occurred, after the main event, in the period covered by the two interferometric pairs; for this reason, they do not affect the deformation signal of the main event. In order to obtain the absolute value of displacement, the following processing procedure was followed.