GSNZ Wellington branch event
GSNZ Branch event
Testing the marine turbidite palaeoseismometer using the 2016 Kaikōura earthquake
Jamie Howarth (VUW) and Alan Orpin (NIWA)
Earthquake records generated from turbidites have been used to produce arguably the longest and most complete records of subduction zone earthquakes around the globe. Such records provide potentially vital information for earthquake forecasting but the basis for them has been vigorously argued by earthquake scientists. Debate about the rigour of turbidite earthquake records exists because there are so few examples where the relationship between the fault(s) that rupture in an earthquake, the spatial extent of strong shaking, and the deposition of turbidites has been observed.
Our work (involving VUW, NIWA, GNS and Kyoto University researchers, funded by EQC, MBIE and Marsden, and published in Nature Geoscience) captures rare observations of turbidity current triggering, leveraged off one of the best measured earthquakes in history, the 2016 Mw7.8 Kaikōura earthquake. Successive field campaigns have densely sampled along and across the axis of submarine canyons in south-eastern Cook Strait that preserve turbidites formed by the earthquake.
Our Wellington Branch presentation will show that turbidites are reliable ‘natural seismometers’. The research highlights that the spatial distributions of turbidites along subduction zones faithfully records the spatial extent of strong shaking offshore. Through repeat sampling, we also hope to quantify the impact of biological mixing on the Kaikōura event deposit, which despite its distinctive characteristics today, is being modified and lost with time. The timeseries generated by repeat sampling has the potential to provide invaluable insights into the features of earthquake triggered turbidites that are ultimately preserved in the sedimentary record.
Not able to attend in person? zoom link: https://vuw.zoom.us/j/93944939970