Fortifying Communication Networks Against Strong Earthquakes Using Real Conduit Damage Records

Natural disasters, particularly strong earthquakes, pose critical risks to communication networks. While previous studies have examined network vulnerability under seismic threats, few have incorporated empirical damage data from past earthquakes for accurate risk assessment. Moreover, existing fortification strategies primarily focus on adding new links, which is rarely feasible for terrestrial networks due to the high costs associated with digging trenches to lay new conduits. Scalability is another major challenge, as conventional methods struggle to handle large-scale regional networks with their thousands of conduits. This paper presents a novel approach to fortifying regional communication networks against strong earthquakes. Our method introduces a graph reduction algorithm that reduces network size by approximately two orders of magnitude, significantly improving scalability. Instead of adding new links, we adopt a multi-edge modeling technique to simulate conduit upgrades, enabling the application of existing link-addition-based fortification methods. Numerical evaluations using real conduit damage inspection data reveal substantial regional and fault-dependent variations in fortification effectiveness; For example, the vulnerability of one regional network can be reduced by 1/3, but another by only 1/10, even if the budget is doubled. Additionally, our method achieves notable computational efficiency, successfully deriving fortification plans for regional networks with up to 8,875 conduits in just 76 seconds.