Illuminating the Pre‐, Co‐, and Post‐Seismic Phases of the 2016 M7.8 Kaikōura Earthquake With 10 Years of Seismicity. Issue 8 (3rd August 2021)

• Record Type: Journal Article
• Authors: Chamberlain, C. J.; Frank, W. B.; Lanza, F.; Townend, J.; Warren‐Smith, E.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-03
• Subjects: Kaikōura earthquake -- matched‐filter -- aftershock -- complex earthquake; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2021JB022304
• Languages: English
• ISSNs: 2169-9313

Abstract

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: (a) the earthquake nucleated on the Humps Fault; (b) 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; (c) 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 (d) 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. Plain Language Summary: The 2016 Kaikōura earthquake in the South Island of New Zealand, is one of the most complex earthquakes reported. While extensive geological work has been undertaken to map the surface faulting in the earthquake, it remains unclear how these faults are linked together at depth. In this paper we document the construction of a dense, long‐duration catalog of earthquakes that occurred on and around the faults that slipped in the Kaikōura earthquake. Using this catalog of 33, 328 earthquakes we are able to illuminate likely sub‐surface links between faults and investigate how these faults slipped before and after the Kaikōura earthquake. We show that offshore faults provide a link between the southern faults, where the earthquake started, and the northern faults, where the highest slip occurred. We also show that the earthquake stopped on faults that had previously slipped in the 2013 Cook Strait earthquakes, and which likely played a role in earthquake arrest. Finally we see no evidence for elevated seismicity on the underlying subduction interface beneath the faults that slipped in the Kaikōura earthquake. Key Points: 10‐year long matched‐filter derived catalog of 33, 328 earthquakes surrounding the 2016 Kaikōura earthquake Observed offshore reverse faulting provides a direct and viable rupture pathway No detectable seismicity occurs on the subduction interface, and any deformation there is aseismic