Guidelines for Performing Hazard-Consistent One-Dimensional Ground Response Analysis for Ground Motion Prediction.

摘要

Along with source and path effects, site response analysis is a vital component of earthquake ground motion prediction. Semi-empirical ground motion prediction equations (GMPEs) include terms for modeling site response that are based on simple metrics of site condition, such as the time-average shear-wave velocity in the upper 30 m of the site (VS30). Because site terms in GMPEs are derived from global ground motion databases and are based on incomplete information on the site condition, their predictions represent average levels of site response observed at sites conditional on VS30. Such predictions are referred to as ergodic. Actual site response at a given site is likely to be different from this global average. Viewed in this context, the actual site response for a particular site and intensity measure can be understood as being the sum of the ergodic estimate from a global model and a (generally unknown) site term (denoted ? S). If the level of site-specific error ( ? S) can be identified and used to adjust the ergodic model, the ground motion analysis becomes more accurate (i.e., bias is removed), and the dispersion of the predicted ground motions is reduced. Therefore, site-specific evaluations of site response are always useful. The question is how that evaluation should be undertaken. In this report, we consider the use of one-dimensional (1D) ground response analysis (GRA) to estimate site-specific site response. We show that previous studies investigating the usefulness of GRA to estimate observed site response (as evaluated from recordings) have achieved mixed success.