# GIS-Based Optimal Route Selection of Submarine Cables Considering Potential Seismic Fault Zones
## 1 Introduction  
The constantly increasing demands for energy and telecommunications worldwide have led to the continuous design, construction and operation of power transmission and telecommunication cables. Such critical lifelines (CLs) are expensive engineering projects that cover hundreds to thousands of kilometers, onshore and/or offshore, while their uninterrupted and safe operation is of paramount importance. On the one hand, submarine power cables, that have a relatively low environmental impact, can contribute to the rapid development of green energy sources, connecting offshore wind and solar farms to onshore power plants, as well as cross-border onshore energy stations [1]. On the other hand, offshore telecommunication cables play a key role in telecommunications and internet, as they can transmit data and information at high speeds around the world. It is noteworthy that almost 99% of communications worldwide are performed through the existing 1.2 million kilometer network of submarine cables [2]. Time delays in transporting information through submarine telecommunication cables could lead to extremefinancial losses. Indicatively, Amazon has reported that every 100 milliseconds of delay could cost up to 1% of profits [2], while the Swiss Federal Institute of Technology has reported that a hypothetical one-week internet blackout in Switzerland could cost a monetary loss of over 1.2% of the country's GDP [3]. The strict environmental policies that have been established due to the intensification of environmental pollution and the increasing awareness for environmental protection, along with the over-increasing demands for cost-feasibility and resilient facilities that work safely and reliably during their lifetime, have necessitated the environmentally-friendly and techno-economically efficient design of CLs [2,4]. In parallel, using mitigation measures to prevent the potential failure of a submarine cable, especially in deep and ultra-deep waters, could be a rather limited and/or expensive solution; therefore highlighting the importance of routing optimization of such infrastructure. Although selecting the optimum route can considerably reduce the probability of failure and the life-cycle costs of the cable, it is usually dominated by a series of critical factors related to environmental, geopolitical, financial and technical aspects [2,5]. In engineering practice, the submarine cable route selection process, which is almost identical to the route selection of offshore pipelines, is manually carried out based on a very time-consuming procedure that relies on the engineering judgment and subjective opinion of the experts [6]. In brief, a suitable corridor is initially defined and graphically designed based on data (from charts, bathymmetric contours, etc.) of the region under consideration. A preliminary survey is carried out along the specific corridor, several reasonable routes are designed, and after processing and evaluating the survey data and ensuring that all hazards or obstacles are completely avoided or eliminated, the optimum cable route is selected. Nevertheless, the application of several project-related advanced criteria, constraints, guidelines, etc., which increase the complexities of the route selection process, are not taken into account, and consequently, this heuristic approach cannot guarantee the optimal path. To overcome this problem, mathematical models and algorithms, unaffected by human bias, have gradually been developed, aiming to facilitate the optimal route selection of CLs [3,7, 8, 9]. Nonetheless, in order to handle the enormous amount of data that are required to perform such complex spatial multi-criteria applications and effectively visualize the corresponding results, the advanced capabilities of geographic information systems (GIS) have been adopted. GIS constitute a powerful tool for multi-criteria analysis, since they provide the efficient methodology of the least-cost path analysis (LCPA).