## 5 Results  
### Calculation of the Geodetically Based Parameters  
#### 5.1.1 Maximum (MaHE) and Minimum (MiHE) Horizontal Extension  
The results of Maximum and Minimum Horizontal Extension parameters (MaHE and MiHE, respectively) are characterized by a wide range of strain field values. In particular, the MaHE values vary between \(-55\) and \(2649\times 10^{-9}\), while the corresponding MiHE values vary between \(-631\) and \(146\times 10^{-9}\), respectively (Figure 4b,c). In addition, the e\({}_{\text{ex}}\), e\({}_{\text{yy}}\), e\({}_{\text{yy}}\) (maximum, minimum, and average) values, and the corresponding uncertainties (Table 2) of the 216 triangles, were calculated, which are necessary for the MaHe and MiHE estimation. The values' distributions reveal that both the MaHE and MiHE absolute maximum values are concentrated along the eastern margin, as well as at the western margin at the northernmost part of the Strymon basin (Figure 4a). The MaHE and MiHE analysis (Figure 4a) indicates the extension dominance, and therefore normal faulting activity, within the greatest part of study area. Particularly, the greatest value distribution is mainly observed in the central part of the study area; the eastern margin region (Nea Zichni village and Serres city) and the western margin northernmost part (Zevgolatio village, located south of the Kerkin Lake). These areas are characterized by significant MaHE values, while the corresponding MiHE absolute values are extremely low, indicating dip-slip, normal faulting activity; the limited number of MiHE values, which are greater than the corresponding MaHE ones, are due to the noise (misinterpretation of geodetic data processing), while they are also inconsistent with the tectonic setting. On both sides of this area, a gradual decrease in the MaHe and MiHE values is documented, while the value difference decreases between MaHE and MiHE at the same time (MaHE values remain greater than the corresponding MiHE ones), indicating oblique-slip, normal faulting activity (e.g., Drama basin, broader Mt Vertiskos and Sidirokastro village areas, etc.). However, the northwestern part of the study area (Mt Belles area) is differentiated from the corresponding neighbor parts, as both MaHE and MiHE values are positive, indicating the dominant, pure extensional regime, expressed by normal faulting. In addition, the MaHE vectors direction (Figure 4a) are almost perpendicular to the faults' and fault zones' strike, confirming both the occurrence and the normal faulting properties of these tectonic structures. Moreover, it should be noted that wherever positive MaHE and negative MiHE values are of the same order, such as at Askos, Sidirokastro, south of Nea Zichni, and locally around Drama, shear prevails; the intensity of shear depends on the order of magnitude of the MaHE-MiHE values. Figure 4: Maximum (MaHE) and Minimum (MiHE) Horizontal Extension in the broader Strymon area: (**a**) MaHE (blue arrows) and MiHE (red arrows) parameters vectors; (**b**) MaHE values grid, based on the interpolation (kriging) geostatistical methodology; (**c**) MiHE values grid, based on the interpolation (kriging) geostatistical methodology. The MaHE and MiHE results were also geostastically processed, implementing interpolation (kriging) methodology in order to facilitate visualization through spatial distribution. Initially, the MaHE geostatistical analysis (Figure 4b) shows three major high-value locations (1700--2649 \(\times\) 10\({}^{-9}\)) located at the eastern margin (two sites) and the northwestern margin (third site). All three locations correlate well with the occurrence of faults and fault zones (e.g., Serres and Tholos-Nea Zichni fault zones), while the medium- and low-value locations (800-1700 \(\times\) 10\({}^{-9}\)) indicate fewer deforming faults or fault zones (e.g., Belles-Kerkini fault zone).