The Case for Using Mean Seismic Hazard

Complete probabilistic seismic hazard analyses incorporate epistemic uncertainties in assumptions, models, and parameters, and lead to a distribution of annual frequency of exceedance versus ground motion amplitude (the “seismic hazard”). For decision making, if a single representation of the seismic hazard is required, it is always preferable to use the mean of this distribution, rather than some other representation, such as a particular fractile. Use of the mean is consistent with modern interpretations of probability and with precedents of safety goals and cost-benefit analysis.