# GIS-Based Optimal Route Selection of Submarine Cables Considering Potential Seismic Fault Zones
## 5 Conclusions  
The current paper presents a smart decision-support tool that can be used for the optimal route selection of submarine cables, since it is capable of assessing whether an examined routing could effectively cross a (seismically) geologically hazardous area. For this purpose, the advanced capabilities of GIS in finding the optimal path between two geographic points are successfully combined with a multi-criteria decision method to transform the qualitative prioritization of the adopted criteria into weight values. In this manner, several cable routes are proposed aiming for length- and cost-minimization. For the routings subjected to tectonic faulting, the problem of fault-cable intersection is quantitatively assessed via realistic numerical models. The resulting cable distress, in terms of strains, is integrated into the GIS model and the optimal route is selected by taking into account the criticality of the problem (i.e., exceedance of the allowable strain limits). The developed numerical models have been verified against experimental results from the literature, whereas the accuracy of the GIS-based routing analysis has been verified against an under-design power transmission cable connecting Greece to Cyprus. The applicability of the smart decision-support tool is presented in two more realistic case studies in the southeastern Mediterranean Sea related to one telecommunication and another power transmission cable. Five different user-defined scenarios have been examined for these case studies, resulting in five alternative cable routings. The proposed routes differ in length, but also in the way that they cross the seismically active fault zones, the potentially unstable steep slopes, as well as the deep and ultra-deep waters. Regarding the telecommunication cable, a useful comparison with the existing routing has been performed. Nevertheless, it should be stressed that the actual comparison with existing engineering problems is indicative, due to the lack of all of the required data and the resulting simplifications. The examined real-life case studies have been used mainly to illustrate the applicability and the effectiveness of the proposed tool. Moreover, some useful conclusions can be derived from the specific applications:  
* Southeastern Mediterranean Sea is prone to offshore geohazards and especially to tectonic faulting, mainly near the coastline of the island of Crete, Greece. This fact highlights the necessity for a very careful seismic design and optimal route selection of crossing critical lifelines;
* All of the alternative routes inevitably pass through extensive zones of moderate-to-large seabed inclinations due to the characteristics of the examined region. However, the assigned weight values corresponding to the seabed inclination in each scenario affect the orientation of the proposed routes within these zones;
* Very long routings have been derived when bathymetry has been given a high importance;
* Assigning high importance to seismic fault zones leads to the shortest routes, which cross almost vertically the fault zones. Nonetheless, relatively high absolute maximum axial strains for medium net bedrock displacements have been observed, regardless of the cable type (i.e., telecommunication or power transmission). Hence, a more sophisticated design is required for seismic events with a higher return period. The process of optimal route selection is not a straightforward task in large-scale engineering projects, even for experienced engineers, and it should be examined on a case-by-case basis, taking into account all important parameters. Certainly, optimum route selection via automated decision-support tools can considerably reduce the probability of failure and the life-cycle costs of the examined lifeline, minimizing the impact of human errors and bias.