The New Zealand Paleoseismic Site Database, Version 1.0

Abstract

Site-specific paleoseismic data are key datasets underpinning the parameterization of large (Mw∼7+) earthquakes on faults in seismic hazard models. For the New Zealand National Seismic Hazard Model 2022 Revision Project (NZ NSHM 2022), a new database, the NZ Paleoseismic Site Database (NZ PSDB), was developed that contains paleoseismic (slip rate, earthquake timings, recurrence interval [RI], and single-event displacement [SED]) data for crustal (upper plate) active faults. The first edition version 1.0 (v.1.0) was modeled on datasets underpinning the Third Uniform California Earthquake Rupture Forecast (UCERF3) and builds on and significantly improves previous NZ compilations. Key improvements include documentation of the data underlying these parameters, such as offset measurements and ages for slip rate, and assignment of quality rankings for key attributes. The NZ PSDB v.1.0 contains 2811 records, subdivided into slip rate (871), earthquake timings (953), and SED (987); the earthquake timings dataset also includes 320 last event and 98 RI records. Because of time constraints, the most effort went into compiling the slip-rate records, in priority from highest to lowest slip rates, and the least amount of time was spent on the SED dataset, prioritizing records from historical earthquakes. The compilation also aimed to obtain as much geographical spread as possible, but the records only lie on a relatively small (maximum, 24%) number of faults and fault sections in the NZ Community Fault Model v.1.0. The most significant spatial gaps are offshore and in the southern and western South Island. The NZ PSDB v.1.0 contains both published and unpublished data, and many sites were relocated using high-resolution basemaps. However, radiocarbon ages were not recalibrated using a consistent calibration curve. Developing a process to efficiently recalibrate radiocarbon ages, as well as filling key data gaps, are current focuses of work toward v.2.0.