Influence of the Uncertainty in Bedrock Characteristics on Seismic Hazard: A Case Study in Italy

Generally, the uniform hazard spectrum obtained from probabilistic seismic hazard analyses (PSHA) is used in conjunction with ground response analysis to estimate the surface seismic hazard at a specific site. In this approach, the reference rock properties of the ground motion prediction equations used in the PSHA must be consistent with the bedrock characteristics at the site under analysis. However, in standard practice, the input motions are determined from PSHA analyses that are conducted for generic reference-rock conditions, which in general are inconsistent with the site-specific bedrock properties. In this paper, we investigate different approaches to correct recorded ground motions in order to be consistent with the site-specific bedrock properties. We use a site in Italy as an example. In addition, we investigate the sensitivity of the correction to the epistemic uncertainties in the evaluation of bedrock characteristics at depth.