This study proposes a novel model to quantitatively evaluate functionality loss in railway network systems during earthquakes and assesses its applicability to a hypothetical railway network system. The model combines seismic fragility functions and restoration curves to assess functionality loss, deriving a time-dependent recovery function to propose a functionality loss model based on earthquake magnitude. The proposed model uses a hypothetical railway network to calculate the overall functionality loss of the network under various earthquake scenarios. The hypothetical railway network was designed with three lines, allowing different routes to remain operational depending on the damaged sections and increasing the diversity of network impact scenarios based on the functionality loss. This model provides a framework for analyzing the functionality loss and recovery processes of railway networks during seismic events and assessing the socioeconomic impacts of earthquakes.

This study proposes a scenario-based framework for quantifying seismic-induced transportation volume loss and economic loss in railway networks by integrating component-level seismic vulnerability assessment with system-level transportation demand analysis. Numerical simulations were performed on an actual regional railway network, comprising major high-speed and conventional lines on the Korean Peninsula and constructed using origin–destination (OD) matrix-based passenger and freight data. Seismic fragility curves and restoration functions were combined to derive seismic functionality loss curves for key structural components, including bridges, embankments, and tunnels. A deterministic earthquake scenario was applied, and spatial ground motion intensity was estimated using regional attenuation relationships and site amplification factors. The resulting functionality degradation was propagated to the network level to quantify transportation volume loss and cumulative economic loss over a 100-day restoration period. Economic loss in this study refers to the direct transportation revenue loss caused by the degradation of network functionality; repair and replacement costs and indirect economic losses are not included. The results indicate that passenger transportation volume on the high-speed line decreased by approximately 60%, resulting in a cumulative economic loss of approximately KRW 391 billion, while freight-oriented conventional lines exhibited transportation losses exceeding 50%. The proposed framework demonstrates how localized structural damage can propagate into system-wide disruption and provides a quantitative basis for restoration prioritization, resource allocation, and seismic risk-informed decision-making for railway infrastructure systems.