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Open AccessArticle

Seismic Imaging of Seafloor Deformation Induced by Impact from Large Submarine Landslide Blocks, Offshore Oregon

1
School of Earth Sciences, The Ohio State University, Columbus, OH 43210, USA
2
ASEE Postdoctoral Research Fellow, US Naval Research Laboratory, Stennis Space Center, Washington, DC 20375, USA
3
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
4
Department of Coastal and Marine Systems Science, Coastal Carolina University, Conway, SC 29528, USA
*
Author to whom correspondence should be addressed.
Geosciences 2019, 9(1), 10; https://doi.org/10.3390/geosciences9010010
Received: 13 November 2018 / Revised: 17 December 2018 / Accepted: 19 December 2018 / Published: 25 December 2018
(This article belongs to the Special Issue Submarine Landslides – Assessing the Stability of Submerged Slopes)
A series of large blocks from the 44-North Slide, offshore Oregon, impacted the seafloor with sufficient force to induce a broad zone of deformation. In 2017, we acquired a seismic profile from the headwall area to the outer toe of this slide. Previous work identified this slide, but it has not been imaged at high resolution before this survey. A striking surficial feature is a collection of blocks that lie downslope from an amphitheater-shaped headwall. The blocks traveled up to 20-km horizontally and about 1200-m vertically down a 13° slope and now cover an area of ~100 km2. The blocks have rough and angular edges that extend up to 400-m above the surrounding seafloor. Seaward of the blocks, a 10-km zone of sediment is deformed, horizontally shortened by 8%. We interpret the strain field to be a result of the dynamic impact forces of the slide. This suggests a high-mobility failure with tsunamigenic potential. It is unclear what preconditioned and triggered this event, however, earthquake-induced failure is one possibility. Gas hydrate dissociation may have also played a role due to the presence of a bottom-simulating reflector beneath the source area. This study underscores the need to understand the dynamic processes of submarine landslides to more accurately estimate their societal impacts. View Full-Text
Keywords: submarine landslide; deformation; Cascadia; Oregon; 44-North submarine landslide; deformation; Cascadia; Oregon; 44-North
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Lenz, B.L.; Sawyer, D.E.; Phrampus, B.; Davenport, K.; Long, A. Seismic Imaging of Seafloor Deformation Induced by Impact from Large Submarine Landslide Blocks, Offshore Oregon. Geosciences 2019, 9, 10.

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