SENSITIVITY OF THE EARTHQUAKE RESPONSE OF A HDRB SEISMICALLY ISOLATED HOSPITAL TO LOCAL CRUSTAL EARTHQUAKES

Abstract

Seismicity in Chile is strongly dominated by subduction megathrust events. Hence, thecharacteristics of ground motions other than those produced by these events are less known.Such is the case for the ground motions generated by crustal faults close to urban areas; oneexample is the San Ramon fault (SRF), which was recently declared as potentially active. Thiswork addresses the sensitivity of the structural response of a High Damping Rubber Bearing (HDRB) seismically isolated hospital in downtown Santiago, Chile, to earthquakes generated onthis Fault. The SRF lies at less than 15 kilometers away from the hospital and there is very little data on its seismogenic capacity and source parameters. Hence, physics-based synthetic earthquake simulations using front-end technologies and bounds for the source parameters areused to predict the impact of such event in the performance of this test structure. The earthquake source parameters considered as uncertain in this study are the event magnitude, averagerupture velocity, and corner frequency. To minimize the number of parameter combinations, a median, an upper, and a lower bound value were selected for each parameter. A set of 16 synthetic ground motion realizations were generated for each parameter combination (27),leading to a total of 432 synthetic records for the analysis. The variability of these records, and the inelastic cyclic response of the HDRBs, are used to compute the expected variations in the earthquake response of the hospital. Building response parameters, such as maximum deformation and shear forces of the isolated layer, inter-story building drifts, and flooraccelerations of the superstructure are used to characterize variability of the hospital response.It is concluded that despite the smaller magnitudes of crustal events relative to the subductionones, they will control some of the response limit states for buildings closer than 15 km to thefault, such as this seismically isolated hospital.