Seismic Risk of Critical Transport Systems: Sensitivity Analysis of the Campania Railway Network to Bradyseism's...

This study examines the impact of epistemic uncertainties on the seismic risk of a critical transport system, the Campania railway network, during the ongoing bradyseismic unrest at Campi Flegrei, south of Italy. Seismic risk is quantified as the length of the railway requiring post-event inspection, an operational proxy for service disruption. A scenario-based risk formulation is adopted, integrating fragility functions for tunnels and masonry arch bridges with a ground-motion model tailored explicitly to volcanic areas. Peak ground acceleration serves as the intensity measure, whereas the annual acceptable probability of failure from the Eurocode informs safety decisions. Epistemic inputs comprise epicenter-location error and azimuth, duration-magnitude error, central-value variability in the ground-motion model, a soil term, and median fragility parameters. A regional sensitivity analysis (SA) using Latin hypercube sampling reveals that uncertainties in epicenter location have a negligible impact on the length of the inspected network. In contrast, hazard- and vulnerability-related variables, including magnitude, ground-motion median, soil class, and fragility medians, exert a strong influence. Increases in magnitude or ground-motion median, or softer soils, markedly expand the network to be inspected, whereas lower component vulnerability, such as bridges and tunnels, reduces it. A variance-based global SA extends the assessment to capture first-order and interaction effects, supporting the prioritization of data collection and model refinement to achieve the greatest reductions in disruption. The methodology provides actionable guidance for infrastructure managers to target and enhance monitoring and mitigation strategies under bradyseismic crises.