A revised paleoseismological record of late Holocene ruptures on the Kekerengu Fault following the 2016 Kaikōura earthquake

Abstract

The Mw 7.8 Kaikōura earthquake of November 14th, 2016 provided rare opportunities to evaluate ground deformation during a large strike-slip earthquake. Following the earthquake, both halves of a displaced paleoseismic trench were re-excavated and extended to test, refine, and extend the known late Holocene chronology of surface rupturing earthquakes on the Kekerengu Fault. 28 organic-bearing samples were collected during these excavations. Of these, six samples provided new 14C ages that could be superimposed on the preferred age model of (Little VDR, Kearse J, Norton K, Benson A, Wang N. 2018. Kekerengu fault, New Zealand: Timing and size of Late Holocene surface ruptures. Bulletin of the Seismological Society of America. 108(3B):1556–1572) to derive an expanded, updated age model of earthquake events on the fault that is now based on 16 dated samples. Including the 2016 earthquake, we recognise six surface rupturing earthquakes on the Kekerengu Fault since ∼2000 cal. B.P. Based on the last five events, our analysis yields an updated estimate of the mean recurrence interval for surface rupturing on the fault of 375± 32 yrs (1σ) since ∼1650 cal. B.P. An older, sixth event (E5) was not included in the preferred age model due to uncertainties in interpretation; however, incorporating this event into an alternative, six-event age model would adjust the recurrence interval estimate to 433 ± 22 yrs (1σ) since ∼2000 cal. B.P.

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