## 4 Discussion
To address this issue in the current study, slope inclination has been classified into five classes (i.e., sub-criteria), ranging from 0\({}^{\circ}\) to 50\({}^{\circ}\), as outlined in Table 1. Quite high weight factors (i.e., 24.3%) have been assigned to slopes with inclinations higher than 10\({}^{\circ}\), while a relatively low weight factor (i.e., 2.8%) has been assigned to low slope inclinations (0\({}^{\circ}\)-10\({}^{\circ}\)). This variation in weight factors ensures that the proposed CI routes pass through almost flat areas and avoid all higher slope inclinations, similar to the strategy that was followed in the design of the existing TAP route in the examined region. As far as the geohazard of primary seismic faulting is concerned, it has to be stressed that only the Kavala-Xanthi-Komotini seismic fault zone located near the Vistonida Lake has been considered as a design criterion. This is due to the fact that the other fault zones had no effect on the CI routing analysis. It is noteworthy that in engineering practice, reducing the fault-CI intersection length (i.e., vertical crossing) is considered preferable for minimizing the risk of CI failure [74]. Nonetheless, in reality, the intersection angle may be affected by uncertainties related to fault rupture characteristics. In addition, in such cases, the fault type plays a crucial role in the type and the magnitude of pipeline strains [75]. Regarding the earthquake-related geohazard of soil liquefaction, two potentially liquefiable areas have been identified. The main difference between these areas is that passing through the potentially liquefiable area 2 may be unfeasible for any engineering infrastructure applications due to potential soil erosion phenomena, as well as socio-economic and other constraints associated with the presence of CI in coastal areas. The coexistence of all the aforementioned earthquake-related geohazards within a relatively small area intensifies the complexity of the routing analysis; thus, the process of optimal route selection is more challenging. Specifically, the primary seismic fault zone acts as a \"physical boundary\" between the flat terrain and steep slopes, while Vistonida Lake stretches from near the primary seismic fault zone to the coastal region. Thus, two narrow \"corridors\" are created between the seismic fault zone, the Vistonida Lake, and the seacoast. In addition, the western end of the main seismic fault zone lies in close proximity to the coast, while the secondary seismic fault zones are perpendicular to the primary fault zone and extend close to the coast. It is evident that avoiding all these fault zones, as well as potentially liquefiable areas, would not lead to an optimal alternative, as it would increase the length of the examined CI and the probability of failure (i.e., passing through steep slopes north of the primary seismic fault zone). As a consequence, alternative CI routings will inevitably cross one, two, or even three seismic fault zones and are expected to pass either within or at the boundaries of potentially liquefiable areas. Results from Figure 7a-d clearly demonstrate that in all the examined \"geotechnical\" scenarios, the criterion of slope inclination played a significant role in routing analysis. Almost all of the proposed routings completely avoid steep slopes located north of the primary seismic fault zone. Similarly, crossing the potentially liquefiable area 1 has been successfully avoided in all routings. However, several of the proposed routings pass through either a part (small or large) or the entire potentially liquefiable area 2. Routes I and II in Figure 7a correspond to scenario 1 (81.8% seismic fault zones) and particularly to sub-scenarios 1.1 and 1.2 (i.e., 81.8% primary and 81.8% 1 st secondary seismic fault zone, respectively). These routes strategically cross either the primary or the 1 st secondary seismic fault zones almost vertically, minimizing the length of the routing exposed to this geohazard.