Coffey GL, Rollins C, Van Dissen RJ, Rhoades DA, Thingbaijam KKS, Clark KJ, Gerstenberger MC, Litchfield NJ, Nicol A. 2022. New Zealand National Seismic Hazard Model 2022: earthquake recurrence derivation from paleoseismic data and probability of detection. Lower Hutt (NZ): GNS Science. 57 p. (GNS Science report; 2022/32). doi:10.21420/2YWK-ZE30.
Abstract
This report presents results of recurrence interval derivation and probability of surface rupture detection studies undertaken for the New Zealand National Seismic Hazard Model 2022 (NSHM) update. Recurrence intervals are one of numerous inversion constraints that are used to constrain the rate of fault ruptures. Here, we utilise earthquake timings, single-event displacement and slip-rate data from the Paleoseismic Site Database, along with geologic and geodetic slip rates from the New Zealand Community Fault Model v1.0 and NSHM Geodetic Deformation Model, to derive recurrence intervals for 81 sites along crustal faults in the NSHM. In these recurrence interval derivations, a weighted combination of recurrence time distributions is used, including lognormal, Brownian Passage Time and Poissonian distributions. Evaluations of recurrence intervals for the Hikurangi subduction zone are estimated from past studies on coastal tectonics, paleotsunami deposits and offshore turbidites. The results of these coastal studies are discussed in this report, and recurrence interval estimations are presented for the Marlborough, Wairarapa Coast and Hawkes Bay sections of the Hikurangi subduction zone. In addition to this, because paleoearthquake timings are used as inversion constraints, it is important to understand what proportion of ‘real world’ earthquakes are reflected in the paleoseismic record used to derive recurrence intervals. Therefore, the probabilities that surface ruptures will be detected at paleoseismic sites was determined both for the Taupō Volcanic Zone (TVZ) and for the rest of the New Zealand region outside of the TVZ as a function of earthquake magnitude, largely following the methodology presented in UCERF3 (Uniform California Earthquake Rupture Forecast, version 3) but utilising New-Zealand-specific estimations of likelihood of surface rupture as a function of magnitude, the results of which are also presented in this report. Compared to UCERF3 results, New Zealand earthquakes outside of the TVZ appear to be significantly less ‘detectable’ than comparable earthquakes in California, whereas earthquakes in the TVZ appear to be more ‘detectable’ than similarly sized earthquakes in California. (The authors)
