Research ArticleOCEANOGRAPHY

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins

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Science Advances  14 Mar 2018:
Vol. 4, no. 3, eaar3748
DOI: 10.1126/sciadv.aar3748
  • Fig. 1 Central New Zealand land and seafloor showing the 1500-km-long Hikurangi Channel that traverses the incoming plate of the subduction margin and feeds the Hikurangi fan drift in the Pacific Ocean east of the North Island.

    The channel is fed by >10 major submarine canyons along the 370-km length of the shelf break, including the Kaikōura Canyon in the south. The Kaikōura earthquake surface fault ruptures are shown in red (14). Blue lines show the major active tectonic structures. Yellow circles show locations where the coseismic turbidite has been sampled, scaled to deposit thickness (T). The bottom right inset shows the detailed morphology of the entrenched Hikurangi Channel with coseismic turbidite sample sites indicated by stars.

  • Fig. 2 Sedimentary evidence for a large-scale sediment gravity flow triggered by the Kaikōura earthquake that originated in the Kaikōura Canyon and traversed the deep-sea Hikurangi Channel.

    (A) Photographic image, x-ray computed tomography (CT), sedimentology (c, clay; z, silt; fs, fine sand; ms, medium sand), and excess 234Th chronology (234Thex) for representative cores from the Hikurangi Channel floor and levee demonstrating very recent turbidite emplacement. The dimensions of the flow are demonstrated by bathymetric (Bathy) profiles showing the height of the Hikurangi Channel levee and core locations that contain the recent flow deposit, which indicate a minimum local flow thickness of 220 m, ~300 km along the channel (B), and 180 m, ~680 km along the channel (C). See Fig. 1 for transect locations.

  • Fig. 3 Coseismic change in the Kaikōura Canyon.

    (A) Digital elevation model (DEM) of the Kaikōura Canyon bathymetry (in grayscale) with overlaid magnitude of erosion and deposition within the canyon, measured by differencing the pre- and post-earthquake bathymetry data sets. Inset panels (top right) show (B) pre-earthquake and (C) post-earthquake bathymetry where coseismic landslides have occurred at the canyon rim (location on the canyon rim indicated by a rectangle). (D) Coarse sediment wave displacement vectors in the lower canyon. Black arrows denote bedform migration vectors. Red arrows show mean vectors for different sections of the sediment wave field (Supplementary Materials). (E) Zoom and long profile of the post-earthquake bathymetry of the sediment waves to illustrate the scale and profile form of these features.

  • Fig. 4 Pre- and post-earthquake seafloor photographs from towed camera transects in the head of the Kaikōura Canyon (locations in the Supplementary Materials).

    (A) Image of the pre-earthquake seafloor in November 2006 showing high densities of benthic foraminifera and sediment bioturbation by infaunal organisms. (B) Image from the same location as (A), captured in January 2017, 10 weeks post-earthquake, showing uniform fine sediments with no signs of benthic invertebrate life. (C) January 2017, rock fall and fine sediments. (D) January 2017, bacterial mat (gray patch on the top right) on sediment surface. Scale bars, 20 cm.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/3/eaar3748/DC1

    Sedimentology

    Chronology

    Sediment volume budget analysis

    Ground motion modeling and recurrence interval estimate

    Canyon geomorphic change analysis

    Biology

    fig. S1. Image, CT slice, and CT number (a bulk density proxy) for cores that contain recently emplaced graded deposits from the Kaikōura Canyon and the Hikurangi Channel and its levee and overbank regions.

    fig. S2. Difference between the pre- and post-earthquake DEMs (color-coded with erosion in red and deposition in blue), overlaid on the shaded bathymetry (grayscale).

    fig. S3. Localized deposition in the mid-canyon region as validation for difference analysis.

    fig. S4. Ground motion modeling and recurrence interval estimate for canyon flushing triggered by widespread failure of the Kaikōura Canyon rim.

    fig. S5. Mean co-registration of optically sensed images and correlation (COSI-corr) results for sediment wave movement with detailed results plotted as compass diagrams by sector.

    fig. S6. The Kaikōura Canyon head showing the location of deep-towed imaging system (DTIS) camera transects run during TAN1701 (red lines) and TAN0616 (yellow lines), multicore deployments during TAN1701 (green filled triangles) and TAN0616 (yellow filled triangles), and Van Veen grab samples collected during TAN0616 (yellow filled circles).

    table S1. Description of core facies from the Kaikōura Canyon and the Hikurangi Channel, levee, and trough.

    table S2. Metadata for multicores collected along the Kaikōura Canyon and the Hikurangi Channel, levee, and trough.

    table S3. Results of 234Th measurements and excess 234Th (234Thex) activities reported in the text.

    table S4. Volume budget calculation details, with lower-bound estimates shown in parentheses.

    References (3438)

  • Supplementary Materials

    This PDF file includes:

    • Sedimentology
    • Chronology
    • Sediment volume budget analysis
    • Ground motion modeling and recurrence interval estimate
    • Canyon geomorphic change analysis
    • Biology
    • fig. S1. Image, CT slice, and CT number (a bulk density proxy) for cores that contain recently emplaced graded deposits from the Kaikōura Canyon and the Hikurangi Channel and its levee and overbank regions.
    • fig. S2. Difference between the pre- and post-earthquake DEMs (color-coded with erosion in red and deposition in blue), overlaid on the shaded bathymetry (grayscale).
    • fig. S3. Localized deposition in the mid-canyon region as validation for difference analysis.
    • fig. S4. Ground motion modeling and recurrence interval estimate for canyon flushing triggered by widespread failure of the Kaikōura Canyon rim.
    • fig. S5. Mean co-registration of optically sensed images and correlation (COSI-corr) results for sediment wave movement with detailed results plotted as compass diagrams by sector.
    • fig. S6. The Kaikōura Canyon head showing the location of deep-towed imaging system (DTIS) camera transects run during TAN1701 (red lines) and TAN0616 (yellow lines), multicore deployments during TAN1701 (green filled triangles)
      and TAN0616 (yellow filled triangles), and Van Veen grab samples collected during TAN0616 (yellow filled circles).
    • table S1. Description of core facies from the Kaikōura Canyon and the Hikurangi Channel, levee, and trough.
    • table S2. Metadata for multicores collected along the Kaikōura Canyon and the Hikurangi Channel, levee, and trough.
    • table S3. Results of 234Th measurements and excess 234Th (234Thex) activities reported in the text.
    • table S4. Volume budget calculation details, with lower-bound estimates shown in parentheses.
    • References (34–38)

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