The effect of bounds on magnitude, source-to-site distance and site condition in PSHA-based ground motion selection

摘要

In this paper, the effect of using bounds on magnitude, source-to-sitedistance, and site condition of prospective records for the purpose of ground motionselection based on probabilistic seismic hazard analysis (PSHA) is investigated. Althoughit is common in ground motion selection to consider bounds on these causal parameters,there is no consistent approach for setting the bounds as a function of the seismic hazardat the site, and no guidance exists on how the bounds should be set considering thedistribution of causal scenarios affecting PSHA results. 36 PSHA cases are considered inthis paper to empirically illustrate the effects of alternative bounds on the characteristicsof selected ground motions, which cover a wide range of deaggregation distributions andsite conditions. The obtained results indicate that the use of excessively narrow boundsencompassing only the dominant causal scenario can lead to ground motion ensembleswith a biased representation for the target hazard. In contrast, the use of relatively widebounds results in ensembles with an appropriate representation for the target intensitymeasure distributions. Quantitative criteria for determining such bounds for generalproblems are provided, which are expected to be sufficient in the majority of problemsencountered in ground motion selection for seismic demand analyses.