# GIS-Based Optimal Route Selection of Submarine Cables Considering Potential Seismic Fault Zones
## 4 Discussion
Route II is a 484 km-long cable routing corresponding to the scenario with realistic weight values (i.e., slopes 30%--bathymetry 7%--seismic fault zones 63%). Seismic fault zones are highly influential, and consequently Route II crosses almost vertically the Cretan-Rhodes ridge and the Hellenic trench. Conversely, the East Mediterranean ridge, which has been assigned a lower rating score, is crossed at an angle different than 90\({}^{\circ}\). Although steep slopes near Egypt are successfully avoided (i.e., crossed vertically for very few kilometers), a notable part of Route II passes through a potentially dangerous high-slope region near the island of Crete. This is due to the impact of the seabed inclination, which is considerably lower than the effect of seismic fault zones. The 472 km-long Route III is the shortest proposed route and it is almost identical to Route II, as they differ only in the way they cross the steep slopes near Egypt. In Route III, the seabed inclination hasbeen assigned a lower weight value (i.e., 9%), compared to the realistic scenario of Route II. As a consequence, Route III has an inclined orientation within the steep slopes near Egypt. Similarly, Route IV and V constitute almost identical routings, differences can be observed in the way they cross the steep slopes near Egypt. Route V, in which the seabed inclination is highly influential, crosses almost vertically both the steep slopes near the island of Crete and the potentially dangerous zone near Egypt. Moreover, Route IV, where the seabed inclination has assigned a moderate weight value, is perpendicularly oriented within the steep slopes near the island of Crete, while a large part of the route passes through the steep slopes north of Egypt. This difference is attributed to the considerable influence of bathymetry, as it can be easily seen that a smaller part of Route IV passes through the deep waters near Egypt, compared to Route V. Finally, although both routes have successfully minimized the intersection with the Hellenic trench (i.e., vertical crossing), the crossing angle with the Cretan-Rhodes ridge differs significantly from 90\({}^{\circ}\). The geomorphology of the examined area is dominated by fault zones that lead to reverse bedrock dislocation of the order of 4 cm per year [73]. Considering that the complete avoidance of the seismically active fault zones is not feasible, and following the engineering practice, the decision-support tool has proposed, among others, cable routings that cross (almost) vertically these critical areas (i.e., for the scenarios where seismic fault zones were assigned great weight values). These routes have been numerically examined against the earthquake-triggered geohazard of fault rupture. It has to be stressed that the problem of reverse fault-cable intersection has not been investigated so far. Conversely, significant research interest has been concentrated on the problem of reverse fault-pipeline intersection, where it has been reported that an almost vertical crossing could lead to early structural failures of CLs even for a very small bedrock dislocation [39]. In the current study, a parametric investigation was carried out considering a net bedrock displacement ranging from 2 cm to 32 cm with a dip angle equal to 60\({}^{\circ}\). Cables that cross shallow waters are generally armored and buried on the seabed, thus increasing the construction costs. At deep and ultra-deep waters, where the threats from human-made hazards are drastically reduced, designers usually prefer light weight cables [6; 24]. However, the tectonic and geomorphological peculiarities of the area under consideration have led the authors to conservatively consider armored cables at both shallow and deep waters and to develop realistic FE models for this type of cable. Figures 12a and 14a present that the absolute maximum axial strains increase almost linearly for relatively small net bedrock displacements, for both the examined submarine cables (i.e., telecommunication and power cables).