An Integrated Earthquake Catalog for Aotearoa New Zealand (Version 1), Event-Type Classifications, and Regional Earthquake Depth Distributions

ABSTRACT We compile an integrated earthquake catalog for Aotearoa New Zealand (NZ) by overwriting event parameters in the national operational seismic catalog (the most complete record of NZ’s seismicity) with refined estimates of event depths, focal mechanisms, locations, and magnitudes from other sources. This was required for several uses in the 2022 NZ National Seismic Hazard Model (NZ NSHM 2022), including distinguishing (classifying) upper-plate, subduction-interface, and intraslab earthquakes to guide the statistics of separate components of the NZ NSHM 2022’s Seismicity Rate Model. Starting from a branch of the operational catalog with standardized event magnitudes, we import revised parameters for 60% of the catalog (including 92% of all 2000–2020 events, 89% of 1951–2020 M ≥ 5.5 events and 84% of 1917–2020 M ≥ 6 events) from relocation studies, literature, the NZ Centroid Moment Tensor database and global catalogs. Next, we classify earthquakes as upper plate, subduction, or intraslab by comparing their depths, locations, and focal mechanisms to the Hikurangi–Kermadec and Puysegur subduction interface geometries and relative plate-motion directions. We show that this event classification would be either highly error-prone or effectively blind in subduction regions if the catalog had not been revised beforehand. Finally, we estimate the depth distribution of upper-plate earthquakes in multiple regions for use in the NZ NSHM 2022 and explore some post-2022 developments of this approach.