The probabilistic on and off fault displacement hazard analysis for high-speed railways crossing the middle Xiaojiang fault zone

The rapid expansion of high-speed railway (HSR) networks in Western China has increased the exposure of linear infrastructure to active faults. This study establishes and applies a probabilistic fault displacement hazard analysis (PFDHA) framework to quantify both on-fault surface rupture and distributed off-fault permanent ground deformation (PGD) hazards for HSR crossings of the Xiaojiang Fault Zone (XJFZ).

A PFDHA framework is developed, integrating a Poissonian seismicity model with spatial rupture randomness. The methodology is applied to the XJFZ, which crosses the Nanning-Kunming (NK) and Shanghai-Kunming (SK) HSR. Permanent displacement hazards are evaluated for 2 probability levels: 10% and 2% probability of exceedance in 50 years.

Through the evaluation of displacement hazards for 50-year exceedance probabilities of 10% and 2%, this study finds that for the NK and SK HSR, permanent displacements at a 10% probability of exceedance range from 1.0 m to 2.9 m, peaking at fault intersections. Comparative analysis shows that traditional deterministic estimates (1.3–2.0 m) generally align with the probabilistic results but fail to capture the full range of risk.

This work adapts PFDHA to linear infrastructure in a tectonically active region of China, explicitly considering both on- and off-fault displacement within engineering-relevant corridors. The integration of regional rupture scaling and segment-based constraints provides a reproducible basis for displacement hazard assessment in HSR planning and retrofit.