Submarine deposition of a subaerial landslide in Taan Fiord, Alaska

Journal of Geophysical Research
By: , and 

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Abstract

A large subaerial landslide entered Taan Fiord, Alaska, on 17 October 2015 producing a tsunami with runup to 193 m. We use LiDAR data to show the slide volume to be 76 + 3/−4 million cubic meters and that 51,000,000 m3 entered Taan Fiord. In 2016, we mapped the fjord with multibeam bathymetry and high‐resolution seismic data. Landslide and postlandslide deposits extend 6 km downfjord, are up to 70 ± 11 m thick, and have a total volume of ~147,000,000 m3. Seismic data image a blocky landslide unit and two units deposited immediately after the landslide. The blocky landslide unit is ~65,000,000 m3. We infer it consists dominantly of subaerially derived material and secondarily of fjord floor sediment. The overlying units are likely megaturbidites presumably deposited within minutes to days after the landslide. We infer that these deposits dominantly consist of fjord floor material mobilized and suspended as the slide entered and traveled downfjord. The lower postlandslide unit is up to 35 ± 6 m thick, and the upper unit is up to 12 ± 3 m thick. These deposits are distinctive and will leave a lasting record of the event. This subaerial‐to‐submarine landslide deposit is distinct from other submarine landslide deposits studied in Alaskan fjords because it has a much greater thickness, larger and more angular blocks, distinctive postlandslide megaturbidites, and a higher‐amplitude acoustic signature of the blocky deposit. The tight constraints on the landslide source and deposit volumes, topography, bathymetry, and tsunami runup heights and flow directions should make this a benchmark site for landslide‐tsunami models.

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Publication type Article
Publication Subtype Journal Article
Title Submarine deposition of a subaerial landslide in Taan Fiord, Alaska
Series title Journal of Geophysical Research
DOI 10.1029/2018JF004608
Volume 123
Issue 10
Year Published 2018
Language English
Publisher American Geophysical Union
Contributing office(s) Alaska Science Center Geology Minerals
Description 21 p.
First page 2443
Last page 2463
Country United States, Canada
State Alaska, Yukon
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