Illuminating the pre-, co-, and post-seismic phases of the 2016 M7.8
Kaikoura earthquake with 10 years of seismicity
Abstract
The 2016 M7.8 Kaikōura earthquake is one of the most complex earthquakes
in recorded history, with significant rupture of at least 21 crustal
faults. Using a matched-filter detection routine, precise
cross-correlation pick corrections, and accurate location and relocation
techniques, we construct a catalog of 33,328 earthquakes between 2009
and 2020 on and adjacent to the faults that ruptured in the Kaikōura
earthquake. We also compute focal mechanisms for 1,755 of the
earthquakes used as templates. Using this catalog we reassess the
rupture pathway of the Kaikōura earthquake. In particular we show that:
(1) the earthquake nucleated on the Humps Fault; (2) there is a likely
linking offshore reverse fault between the southern fault system and the
Papatea Fault, which could explain the anomalously high slip on the
Papatea Fault; (3) the faults that ruptured in the 2013 Cook Strait
sequence were reactivated by the Kaikōura earthquake and may have played
a role in the termination of the earthquake; and (4) no seismicity on an
underlying subduction interface is observed beneath almost all of the
ruptured region suggesting that if deformation did occur on the plate
interface then it occurred aseismically and did not play a significant
role in generating co-seismic ground motion.