Geomorphic impacts of earthquake-triggered flushing of Kaikōura Canyon following the 14 November 2016 M7.8 Kaikōura Earthquake, New Zealand
Abstract
Repeat seafloor measurements and targeted sampling show that the November 2016 Mw 7.8 Kaikōura earthquake triggered widespread landslides in a large-scale bedrock submarine canyon and generated a powerful "canyon-flushing" event and turbidity current that travelled > 680 km along one of the world's longest deep-sea channels, the Hikurangi Channel. To our knowledge these observations provide the first direct quantification of seafloor landscape change and sediment flux from an earthquake-triggered, full canyon flushing event. Our results augment observations from smaller scale turbidity currents within the confines of large submarine canyons (e.g. in the Monterey Canyon, California, USA) that are shown to move stored material within canyons but not export sediment to the deep ocean or erode into the underlying substrates. The frequency of Kaikōura Canyon flushing events is 140 years, calculated from back analysis of predicted strong ground motion required to trigger sediment failure, and supported by turbidite frequency derived from 14C dating of pre Kaikōura earthquake sediment cores. Significant geomorphic change occurred within the canyon including erosion up to 60m depth in the upper canyon, scour hole formation into bedrock in the middle reaches, and down-canyon movement of mega-scale bedforms in the lower canyon constructed of gravel to boulder sized material. The observed tens of meters of erosion into bedrock in the mid canyon combined with the calculated flushing frequency indicates an overall canyon incision rate of 40 mm y-1, substantially higher than most terrestrial rivers. The event synchronously transferred an estimated 850 Mt of sediment and 7 Mt of organic carbon to the deep ocean. Our observations demonstrate that earthquake-triggered canyon flushing is the primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS11A..05H
- Keywords:
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- 1824 Geomorphology: general;
- HYDROLOGYDE: 3002 Continental shelf and slope processes;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3045 Seafloor morphology;
- geology;
- and geophysics;
- MARINE GEOLOGY AND GEOPHYSICS