Earthquake Response Sensitivity of HDRB Base-Isolated Hospitals to the Crustal San Ramón Fault in Santiago, Chile

Abstract

Subduction megathrust events dominate seismicity in Chile, leading to a less comprehensive understanding of the hazard posed by crustal faults. One such source is the San Ramón fault (SRF), a potentially active fault at the eastern border of the Metropolitan Region of Santiago. This study assesses the seismic performance of three modern hospitals seismically isolated with high damping rubber bearings, located 7–24 km from the SRF trace. Their responses were evaluated using nonlinear 3D finite element models subjected to a suite of 432 synthetic ground motions. To account for the uncertainty in the seismogenic capacity of the SRF, these physics-based simulations systematically vary key source parameters, including event magnitude, average rupture velocity, and corner frequency. For facilities near the fault, the results show critical performance failures. Isolation systems are prone to pounding as displacements exceed their design limits, while large vertical accelerations cause a high probability of tensile forces in the bearings. Furthermore, interstory drifts and floor accelerations in the superstructures exceed the thresholds required to maintain continuous operation. These findings reveal that even the new generation of seismically isolated hospitals is critically vulnerable to near-fault crustal earthquakes if not explicitly designed for them. This unaccounted-for seismic hazard highlights an urgent need for comprehensive risk re-assessment and the development of targeted mitigation strategies in Santiago and other cities facing similar hazards.