A Repeating Earthquake Catalog for New Zealand

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

Repeating earthquakes have the potential to elucidate dynamic processes at depth on faults. In particular, recent work has shown that repeating earthquakes may provide a means for measuring deformation rates at depth. Furthermore, slip-rates derived from repeating earthquakes appear to change throughout the seismic cycle. New Zealand’s diverse tectonics provide an ideal setting to test ideas on how we interpret repeating seismicity. Thanks to the efforts of New Zealand’s national seismograph network, GeoNet, New Zealand has an incredible archive of digital data spanning from the late 1980s. This long-duration dataset permits the study of repeating earthquakes over a range of inter-event times and magnitudes.

We have analysed the New Zealand earthquake catalog from 1987 to 2018 to look for repeating earthquakes and are currently building the first nationwide catalog of repeating seismicity for New Zealand. During this period more than 500,000 earthquakes were cataloged, of which we analyse the 391,688 for which digital data and seismograph response information are available. From this initial catalog we cross-correlate all available channels for nearby events to obtain a catalog of possible repeaters. This catalog contains a strong contribution from swarms, aftershock sequences and volcano seismicity as well as classical repeating events. Repeaters cluster on the Fiordland subduction zone, at the transition from southern to central Alpine Fault, and at various locations along the northern Hikurangi subduction margin. Deep repeating seismicity occurs beneath the Taupo volcanic zone, as well as appearing to locate on the deep extent of the southern Hikurangi margin. Further work remains to precisely relocate all events and separate true repeaters from clustered seismicity.

Presenting Author: Calum J. Chamberlain

Authors