Submarine landslide kinematics derived from high-resolution imaging in Port Valdez, Alaska

Journal of Geophysical Research - Solid Earth
By: , and 

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Abstract

Submarine landslides caused by strong ground shaking during the M9.2 1964 Great Alaska earthquake generated a tsunami that destroyed much of the old town of Valdez, Alaska, and was responsible for 32 deaths at that location. We explore structural details of the 1964 landslide deposit, as well as landslide deposits from earlier events, in order to characterize kinematics of the landslide process. We present a new high‐resolution seismic reflection data set that images the 1964 landslide deposit and six pre‐1964 deposits with great detail. These deposits are represented by thick packages (~7–23 m) of debris within >500 m of fjord sedimentation above basement. Internal slide structures are associated with distinctive landslide failure mechanisms, including detailed erosional and depositional features and structures resolved within both landslide blocks and distal debris flow layers. Based on comparisons of deposit volume from subbottom structure and differenced bathymetry, we refine prior interpretations of the source of failed material. New data show evidence for basal erosion and reworking of fjord‐floor sedimentation. Additionally, material comprising the 1964 landslide appears to have been translated and deformed by lateral thrusting, rather than having been sourced entirely from upslope evacuation zones. Taking into account these complexities in depositional patterns, we show variations in slide size through Holocene time and relate the history of landslides to the paleoseismic record. Collectively, these new observations demonstrate that Port Valdez has a repeated history of large submarine landslides, which are likely associated with large megathrust earthquakes.

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Publication type Article
Publication Subtype Journal Article
Title Submarine landslide kinematics derived from high-resolution imaging in Port Valdez, Alaska
Series title Journal of Geophysical Research - Solid Earth
DOI 10.1029/2019JB018007
Volume 125
Issue 7
Year Published 2020
Language English
Publisher American Geophysical Union
Contributing office(s) Alaska Science Center Geology Minerals, Pacific Coastal and Marine Science Center
Description e2019JB018007, 20 p.
Country United States
State Alaska
Other Geospatial Port Valdez
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