Regional-Scale Multi-Hazard Assessment of Earthquake-Induced Road Network Disruption

Recent earthquakes have shown that earthquake-induced landslides and liquefaction can severely disrupt transportation systems and generate significant direct and indirect losses. Still, these secondary hazards are rarely incorporated into regional road-network disruption assessments. This paper presents a scenario-based multi-hazard methodology, implemented in the OpenQuake-engine, for integrating ground shaking, earthquake-induced landslides, and liquefaction into transportation-network analysis. The workflow combines hazard modelling, component-level damage and operability assessment, and network-based performance metrics. The methodology is demonstrated for the major road network of Southern Portugal using three representative earthquake scenarios. The results show that ground shaking is the dominant driver of regional disruption, but liquefaction and landslides can contribute locally to asset non-operationality and connectivity loss, particularly where susceptible ground conditions coincide with critical network links. The results also show that multi-hazard impacts are not simply additive, because network disruption depends on the spatial configuration and overlap of affected components. Compared with ground-shaking-only analyses, the proposed approach provides a more complete representation of road-network disruption and helps identify locations where secondary hazards may compromise network redundancy and emergency accessibility.