Methods for evaluating the significance and importance of differences amongst probabilistic seismic hazard results for engineering and risk analyses: A review and insights

When new seismic hazard models are published it is natural to compare them to existing models for the same location. This type of comparison routinely indicates differences between the assessed hazards in the various models. The question that then arises is whether these differences are scientifically significant, given the large epistemic uncertainties inherent in all seismic hazard models, or practically important, given the use of hazard models as inputs to risk and engineering calculations. A difference that exceeds a given threshold could mean that building codes may need updating, risk models for insurance purposes may need to be revised, or emergency management procedures revisited. In the current literature there is little guidance on what constitutes a significant or important difference, which can lead to lengthy discussions amongst hazard analysts and end users. This study reviews proposals in the literature on this topic and examines how applicable these proposals are for several sites considering various seismic hazards models for each site, including the two European Seismic Hazard Models of 2013 and 2020. The implications of differences in hazard for risk and engineering purposes are also examined to understand how important such differences are for potential end users of seismic hazard models. Based on this, we discuss the relevance of such methods to determine the scientific significance and practical importance of differences between seismic hazard models and identify some open questions. Finally, we make some recommendations for the future.