A time-dependent seismic hazard model following the Kaikōura M7.8 earthquake

ABSTRACT Following the 2016 M7.8 Kaikōura earthquake, a time-varying seismic hazard model (KSHM) was developed to inform decision-making for the reinstatement of road and rail networks in the northern South Island. The source model is the sum of a gridded 100-year earthquake clustering model and an updated fault source model. The gridded model comprises long-term, medium-term and short-term components. The 100-year gridded model is constructed as the sum of 100 annual forecasts. A discounting method trades off expected earthquake occurrences of the distant future against those of the near future. The fault source model includes updates to account for newly revealed faults that ruptured in the Kaikōura earthquake and other recently obtained new information, and new time-varying probabilities of rupture for four fault segments. Two different characterisations of the Hikurangi subduction interface are incorporated via a logic tree, with weights determined by an expert panel. A suite of ground motion prediction equations contribute to a logic tree in order to account for epistemic uncertainties in source modelling for each of four tectonic region types. Here, we compare the resulting hazard estimates with the 2010 National Seismic hazard Model and recorded motions in past New Zealand and global earthquakes.