## 7 Conclusions  
Space geodetic techniques bring to light how much and in which manner the upper crust is deformed, and, consequently, how tectonic processes are occurring at present. The application of this analysis in the broader Strymon basin, which is based on the qualitative and quantitative calculation of specific geodetic strain parameters (MaHE, MiHE, MaxSS, and AS), strongly suggests that the study area is characterized by low predominantly extensional deformation, an outcome that is also supported by the poor seismic activity and the low slip-rate faults. Hence, considering the GNSS results, combined with the InSAR analysis, the following concluding remarks are drawn:  
1. A dominant N-S (up to NE-SW) direction of extension is documented by the geodetic parameters, which is responsible for the major E-W (up to NW-SE) fault zones observed throughout the Strymon basin;
2. The eastern margin of Strymon basin includes the most tectonically active structures (e.g., Serres and Tholos-Nea Zichni dip-slip, normal fault zones) of the study area; the Belles-Kerkini dip-slip, normal fault zone, located at the northwestern part, may be considered potentially active. It is noted that the Serres fault zone accommodates the greatest strain within the study area;
3. The southwestern margin of the Strymon basin shows much lower, but not negligible, deformation. This deformation could be associated with the low and scattered seismicity in this area. According to the deformation indices, shear faulting is the expected kinematics;
4. GNSS data indicate some moderate strain rates at the northwest boundary of the Strymon basin (southeast of Lake Kerkini and near Zevgolatio), implying that some are highlighted by both deformational parameters and seismic activity;
5. The strain parameters suggest that the Serres fault zone should be further extended to the west, indicating that its length has been underestimated;
6. The geotectonically related GNSS results (V parameter) highlight the SSE motion of the study area, being consistent with the Aegean microplate motion, which moves towards the Hellenic Subduction Zone;
7. No horizontal rates have been traced by InSAR in the E-W direction along the study area; if they do exist, they would be below resolution (less than 2 mm/yr);
8. Vertical InSAR subsidence of a few mm/yr is traced in the immediate hanging wall of the Serres fault zone, within the Quaternary basin; however, it is mainly attributed to non-tectonic effects such as groundwater extraction;
9. The detection of potential active faults in areas where geodetic strain is recorded, but active faults have not been mapped, or the prolongation of fault traces in areas where local conditions prevent direct observations, highlight the essential role of satellite geodesy and InSAR in the process of seismic hazard assessment, as it may decisively contribute to the determination of fault properties. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app12189391/s1](https://www.mdpi.com/article/10.3390/app12189391/s1)]([https://www.mdpi.com/article/10.3390/app12189391/s1](https://www.mdpi.com/article/10.3390/app12189391/s1)), Figure S1: C (vertical component), for GNSS sites located over the InSAR processing extend. The closest PS target to the GNSS sites, within a search radius of 200 m, was considered. The corresponding measurements' uncertainties for each technique are also shown (error bars). ; Figure S2: Uncertainties of PSI displacement rates for Sentinel-1 ascending track 102 (2015-2020); Figure S3: Uncertainties of PSI displacement rates for Sentinel-1 descending track 7 (2015-2020); Figure S4: Vertical displacement rates for the period 2015-2020 at 200 m spatial resolution, as derived by combining ascending and descending PSI measurements. Positive values correspond to uplift, whereas negative values to subsidence; Figure S5: E-W displacement rates for the period 2015-2020 at 200 m spatial resolution, as derived by combining ascending and descending PSI measurements.