Expert Judgment in the 2022 Aotearoa New Zealand National Seismic Hazard Model

Abstract

The 2022 revision of the New Zealand National Seismic Hazard Model—Te Tauira Matapae Pūmate Rū i Aotearoa (NZ NSHM 2022) is, like other regional and national seismic hazard models, a collection of many component models that are combined via logic trees to calculate various parameters of seismic hazard. Developing, selecting, and combining component models for the NZ NSHM 2022 requires expert judgment. Informal and unstructured use of expert judgment can lead to biases. Drawing on a broad body of literature on potential biases in expert judgment and how to mitigate them, we used three approaches to incorporate expert judgment with the aim to minimize biases and understand uncertainty in seismic hazard results. The first approach applied two closely aligned group structures—the Science Team Working Groups and the Technical Advisory Group (TAG). The groups between them defined the project and made the scientific decisions necessary to produce the final model. Second, the TAG provided the function of a participatory review panel, in which the reviewers of the NSHM were actively engaged throughout the project. The third approach was performance-based weighting of expert assessments, which was applied to the weighting of the logic trees. It involved asking experts so-called calibration questions with known answers, which were relevant to the questions of interest, that is, the logic-tree weights. Each expert provided their best estimates with uncertainty, from which calibration and information scores were calculated. The scores were used to weight the experts’ assessments. The combined approach to incorporating expert judgment was intended to provide a robust and well-reviewed application of seismic hazard analysis for Aotearoa, New Zealand. Robust expert judgment processes are critical to any large science project, and our approach may provide learnings and insights for others.