Site Response Effects on Partially Ergodic PSHA

Abstract

Near surface materials play an important role in modifying seismic waves, hence the uncertainty in their properties is significant to the surface ground motion uncertainty. A partially non-ergodic approach that removes the uncertainty associated with site response from the ergodic ground motion prediction equation, and then accounts for the epistemic site response uncertainty within a particular site is presented. Probabilistic seismic hazard analyses (PSHA) results show that for better characterized sites the uncertainty on surface ground motion can be drastically reduced with respect to the ergodic prediction. This effect is stressed when long return periods are examined. The presented approach also produces a reduction on the ground motion prediction bias due to the site-specific modeling of site response.