Rollins C, Rhoades DA, Rastin SJ, Gerstenberger MC, Christophersen A, Thingbaijam KKS, Van Dissen RJ, Graham K, Fraser J. 2022. The magnitude-frequency distributions of earthquakes in the greater New Zealand region and along the Hikurangi–Kermadec and Puysegur subduction zones, and their uncertainties, with application to the 2022 New Zealand National Seismic Hazard Model. Lower Hutt (NZ): GNS Science. 77 p. (GNS Science report; 2022/48). doi:10.21420/SXPX-8C68.
Abstract
For use in the Seismicity Rate Model (SRM) component of the 2022 New Zealand National Seismic Hazard Model, we estimate the total magnitude-frequency distribution (MFD) of earthquakes in the greater New Zealand region and along the Hikurangi–Kermadec and Puysegur subduction zones. The former is a key input into multiple components of the SRM in the onshore and near-shore regions, while the latter is a key input into models of earthquake rupture rates on the subduction zones. In the SRM, the MFDs are parametrised by a b-value (which describes the relative rates of small and large earthquakes) and by the annual rate of M ≥5 earthquakes, here called the N-value. To estimate these parameters and their uncertainties in the above settings, we use a variant of the New Zealand earthquake catalogue that includes improved depth information, focal mechanisms and complete coverage of the Hikurangi–Kermadec region, among other features. Adapting an approach used previously in California, we estimate the MFD of earthquakes in the near-shore region incorporating data back to 1843, balanced with the better data in the more recent part of the instrumental catalogue. This method estimates both the mean earthquake rate and its uncertainty, and we supplement it with an alternative estimate of the rate uncertainty that is based on the rate variability in the catalogue over a range of shorter timespans. We estimate the MFDs on the Hikurangi–Kermadec and Puysegur subduction zones using a simplified version of the method used in the near-shore region, with more recent data. Finally, we describe a globally based method to estimate the potential earthquake rate uncertainty on the Hikurangi–Kermadec subduction zone. (The authors)
