2:00 PM - 2:15 PM
[SCG49-02] Priorities for improving seismic hazard modelling in Aotearoa New Zealand
Keywords:seismic hazard, subduction zone, soil non-linearity, time-dependence, New Zealand
In late 2022 a significant revision of the New Zealand National Seismic Hazard Model was released. An important emphasis of this new model was developing a more thorough understanding of the uncertainties impacting the model and propagating those uncertainties through to the final forecast distribution. In this processes key uncertainties impacting the uses of the model were identified; these included uncertainties that were modelled and also those that could not be objectively quantified or otherwise included. These uncertainties have shaped the current work we are undertaking towards the next revision of the NSHM. In working with the NZ building code committee the uncertainty, and potential bias, introduced by the poor constraints on soil non-linearity for very strong shaking was identified as a key concern for building code uses. From the rupture modelling components the uncertainty coming from the variability in the overall rate was the greatest contributor, and nearly equivalent to the ground motion uncertainty in some cases. Additionally, the lack of short-term time dependence and relatively long forecast time-window (100 years) does not suit the needs of the insurance and reinsurance industries (introducing uncertainty). An important uncertainty that was not explicitly modelled in the 2022 model is the potential for the Hikurangi subduction interface to rupture jointly with the many crustal faults it underpins at a shallow depth; evidence from historical events suggests this is a possibility. In this presentation I will present these and other key uncertainties and our ongoing work to improve our understanding of the topics.