# GIS-Based Optimal Route Selection of Submarine Cables Considering Potential Seismic Fault Zones
## 1 Introduction
The LCPA, which was introduced in 1957 by [PERSON] [10], is usually applied to determine the optimal path between two points, and it can be additionally combined with advanced multi-criteria decision methods (MCDMs), such as the analytical hierarchy process (AHP). The integration of MCDM and GIS has been successfully applied for land-use [11] and site suitability analysis [12], urban planning and development problems [13,14], as well as for the route selection of CLs (e.g., [2,15,16]). LCPA can handle several spatial criteria related to the effectiveness maximization and cost minimization of the CLs in a computationally efficient manner [17]. The selected criteria can be weighted in accordance with the requirements and constraints of the project (budget, accessibility, etc.). Several studies have reported the application of GIS in the optimal route selection of submarine CLs, reducing project costs by up to 30% [7,18, 19, 20, 21]. In addition, it is worth noting that the route optimization of offshore large-scale engineering projects is suggested by international standards, such as the guidelines of the American Bureau of Shipping (ABS) [22]. Nonetheless, seismicity and the subsequent earthquake-triggered geohazards, such as slope instabilities, soil liquefaction and tectonic and non-tectonic faulting [23] (which have a high probability of occurrence during the lifetime of the infrastructure) constitute crucial factors during the process of optimal route selection, since they may have a remarkable impact on the structural performance of a CL [6,24]. These factors can be underestimated or improperly taken into account during the optimal route selection of CLs if they are treatedbased only on engineering judgment. In particular, decisions related to disaster planning are often taken by the stakeholders, either manually or by utilizing the aforementioned mathematical models and/or the GIS-based techniques based on heuristics and rules of thumb [25]. Consequently, a route can be selected that either completely avoids all of the geologically hazardous areas or crosses them without adequately assessing the potential structural distress [26]. On the one hand, the complete avoidance of such areas constitutes an over-conservative approach, which might lead to economically unfeasible routings, as the length (and therefore the cost) of the CL may considerably increase. On the other hand, crossing geologically hazardous areas is a challenging issue that may detrimently affect the integrity and functionality of the CL, while costly and impractical mitigation measures may be required. Indicatively, many severe failures of submarine cables due to earthquake events and earthquake-related geohazards have been reported during the last decades. For instance, the earthquake-triggered geohazards due to the 6.8-magnitude Boumerdes earthquake, that occurred in Algeria in 2003, damaged at least six submarine fiber-optic cables, thus affecting the transmission of data and information throughout the Mediterranean region [24]. The 7.1-magnitude Pingtung earthquake in Southern Taiwan in 2006 caused an extensive internet and telecommunications disruption in South East Asia, as more than 20 offshore fiber-optic cables were broken or suffered severe damages [27]. The 2011 severe earthquake in East Japan affected a network of telecommunication cables of a total length greater than 2500 km [28]. Obviously, submarine cables are vulnerable to severe earthquakes and the resulting soil deformations due to earthquake-triggered geohazards. Considerable research effort has been concentrated on the cost-effective and resilient cable route selection considering earthquake hazard information and likelihood maps in conjunction with stochastic models for the occurrence of the earthquakes [5; 29; 30; 31]. However, the problem of fault-cable intersection constitutes a challenging topic that has not been thoroughly investigated, thus, few relevant publications can be found in the literature. [PERSON] et al.