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Version 2 of an Integrated Earthquake Catalog for Aotearoa New Zealand and 3D Earthquake-depth Models

Description: 

In 2021-22, for the 2022 New Zealand National Seismic Hazard Model (NZ NSHM), we compiled version 1 of an integrated earthquake catalog for New Zealand by merging the GeoNet operational seismic catalog (the most complete record of NZ’s seismicity) with standardized event magnitudes, relocations, focal mechanisms, and global catalogs. This integrated catalog, and its improved event parameters, are needed for several uses in the NZ NSHM including:

- classifying earthquakes as in the upper plate, on the Hikurangi or Puysegur subduction zone, or in one of the subducting slabs, using event depths and focal mechanisms;

- estimating the magnitude-frequency distributions of those five tectonic regimes using the event classifications and the standardized magnitudes;

- estimating the earthquake depth distribution in various regions of NZ for the NSHM’s Distributed Seismicity Model (DSM), and underpinning the hybrid spatial earthquake-rate forecasts that go into the DSM;

- estimating the geologic detectability of NZ earthquakes as a function of magnitude, used in the NSHM’s Inversion Fault Model (IFM).

Version 1 of the integrated earthquake catalog covered through the end of 2020. For the 2028 release of the one-year time-dependent NZ NSHM, we are preparing version 2, through several lines of work:

- adding 2021-2025 earthquakes (eventually 2021-2027) with standardized magnitudes (and relocated depths, locations and focal mechanisms where possible);

- adding relocations and focal mechanisms for several thousand pre-2000 earthquakes from ESNZ archives and literature;

- adding new and previously unused large-scale relocations of post-2000 events;

- adding machine-learning catalogs that fill in missing events from recent aftershock sequences and sparsely instrumented regions;

- improving the record of offshore earthquakes on the Hikurangi and Puysegur subduction zones using updated global catalogs.

Here, we will present current progress on version 2 of the integrated catalog and resulting 3D models of the depth distribution of earthquakes throughout Aotearoa New Zealand.

Session: Advancing Seismic Hazard and Risk Assessment through Multi-Disciplinary Approaches - I

Type: Oral

Date: 4/15/2026

Presentation Time: 10:30 AM (local time)

Presenting Author: Chris Rollins

Student Presenter: No

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