A Repeating Earthquake Catalog From 2003 to 2020 for the Raukumara Peninsula, Northern Hikurangi Subduction Margin, New Zealand

Repeating earthquakes provide a novel way of monitoring how stresses load faults between large earthquakes. To date, however, and despite the availability of long-duration, high-quality seismological datasets, little attention has been paid to tectonic repeating earthquakes in New Zealand. We develop a workflow and composite criterion for identifying repeating earthquakes in New Zealand, using data from the GeoNet permanent seismic network, and present New Zealand's first decadal-scale repeating earthquake catalog. For events to be identified as repeating in this study, two or more events must have a normalized cross-correlation of at least 0.95 at two or more seismic stations, when calculated for 75% of the earthquake coda. By applying our composite criterion to seismicity around the Raukumara Peninsula, northern Hikurangi subduction margin, we have identified 61 repeating earthquake families occurring between 2003 and 2020, consisting of 347 individual earthquakes. These families have a magnitude range of M-L 1.7-5.2 and recurrence intervals of < 1 to similar to 7 yrs. Repeating earthquakes in 9 of the 11 regional groups identified in this study coincide spatiotemporally with previously identified slow-slip events and tremor. However, the responses shown to slow-slip are not consistent within families or within regional groups.

Automated summary

This study identified and analyzed repeating earthquakes in New Zealand, revealing 61 repeating earthquake families occurring between 2003 and 2020. These families have a range in magnitude and recurrence intervals, showing spatiotemporal correlation with known slow-slip events and tremor, but inconsistency in responses.