Accommodating ~9 m of dextral slip on the Kekerengu Fault through ground deformation during the Mw 7.8 Kaikōura Earthquake, November 2016

Abstract

The Mw 7.8 Kaikōura earthquake of November 14th 2016 provided unprecedented opportunities to understand how the ground deforms during large magnitude strike-slip earthquakes. The re-excavation and extension of both halves of a displaced paleoseismic trench following this earthquake provided an opportunity to test, refine, and extend back in time the known late Holocene chronology of surface rupturing earthquakes on the Kekerengu Fault. As part of this thesis, 28 organic-bearing samples were collected from a suite of new paleoseismic trenches. Six of these samples were added to the preferred age model from Little et al. (2018); this updated age model is now based on 16 total samples. Including the 2016 earthquake, six surface rupturing earthquakes since ~2000 cal. B.P. are now identified and dated on the Kekerengu Fault. Based on the latest five events (E0 to E4), this analysis yields an updated mean recurrence interval estimate for the Kekerengu Fault of 375 ± 32 yrs (1σ) since ~1650 cal. B.P. The older, sixth event (E5) is not included in the preferred model, as it may not have directly preceded E4; however, if this additional event is incorporated into an alternative age model that embraces all six identified events, the mean recurrence interval estimate (considered a maximum) calculated is 433 ± 22 yrs (1σ) since ~2000 cal. B.P.

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