Assessing the impact of systemic heterogeneity on failure propagation across interdependent critical infrastructure systems

The systemic heterogeneity between different critical infrastructure systems (CISs) can significantly influence the failure propagation process across the systems. For instance, when power supply systems are affected by an earthquake, physical damages mainly occur at nodes and seldom occur at links, since the cables are flexible enough to withstand the impacts. Water supply systems on the other hand are prone to experience physical damages at both nodes and links. However, despite the increasing volume of literature that examines failure propagation risks across interdependent CISs, only few studies have accounted for various systemic heterogeneity factors (HFs) and their potential impact on cascading failures. The aim of this study is to reveal and quantify the significance of such impact, for which a four-step approach is introduced. A case study was conducted, which examined the impact of three HFs on failure propagation across two interdependent power and water supply systems in the event of a simulated earthquake. Seven improved models were developed and their respective simulation results were compared. The comparison of simulation results from the baseline model and improved models revealed that the impact of the simulated earthquake disaster on CISs would be significantly misestimated if the HFs were not considered, and that each HF impacted the failure propagation in a different way. The proposed approach and the findings in the case study are expected to uncover the drawbacks in current CISs failure propagation models, and provide a foundation for the development of more reliable failure propagation modeling approaches in future research.