Matt Gerstenberger
(Seismologist/NSHM Lead, GNS Science |Te Pῡ Ao, Newzealand)
【Title】
The New Zealand National Seismic Hazard Model: modelling uncertainty and implications for its use
【Abstract】
In 2022 a significant revision of the New Zealand National Seismic Hazard Model (NSHM) was released. The revision was a significant change to all components of the model and resulted in a large increase in hazard across New Zealand. An important focus of the revision was on the understanding and modelling of uncertainties that impact that resultant hazard forecasts. Following a traditional probabilistic seismic hazard analysis approach, all uncertainties are split into two categories: 1) aleatory, which is defined as inherent randomness in earthquake processes; and 2) epistemic, which is defined as uncertainty in our knowledge. The distinction between the two is not always clear cut, yet the choice in how any parameter is modelled has clear implications for decisions based on the NSHM. In NZ the NSHM has significant uptake across government and private sectors. It underpins, for example, the NZ building code, large engineering projects, long-term planning and the insurance industry. In this talk I will discuss how we model the uncertainty, what some of the key uncertainties are (e.g., non-Poisson occurrence rates, and ground shaking), and how these uncertainties are passed on and used, or not used, in decision making. Importantly, I will discuss how the choice in how the uncertainty is modelled, can lead to the uncertainty being ignored or, potentially, over-emphasised.
