Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska
Can a predominantly creeping segment of a subduction zone generate a great (M  > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-kn...
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ftunivrhodeislan:oai:digitalcommons.uri.edu:geo_facpubs-1006 2024-09-15T18:07:34+00:00 Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska Witter, Robert C. Briggs, Richard W. Engelhart, Simon E. Gelfenbaum, Guy Koehler, Richard D. Barnhart, William D. 2014-04-09T07:00:00Z application/pdf https://digitalcommons.uri.edu/geo_facpubs/7 https://doi.org/10.1002/2014GL059393 https://digitalcommons.uri.edu/context/geo_facpubs/article/1006/viewcontent/Witter_et_al_2014_Geophysical_Research_Letters.pdf unknown DigitalCommons@URI https://digitalcommons.uri.edu/geo_facpubs/7 doi:10.1002/2014GL059393 https://digitalcommons.uri.edu/context/geo_facpubs/article/1006/viewcontent/Witter_et_al_2014_Geophysical_Research_Letters.pdf Geosciences Faculty Publications text 2014 ftunivrhodeislan https://doi.org/10.1002/2014GL059393 2024-08-21T00:09:33Z Can a predominantly creeping segment of a subduction zone generate a great (M  > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (≤0.3 m) to perturb the onshore geologic record. Text glacier Alaska University of Rhode Island: DigitalCommons@URI Geophysical Research Letters 41 7 2359 2367 |
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Open Polar |
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University of Rhode Island: DigitalCommons@URI |
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ftunivrhodeislan |
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unknown |
description |
Can a predominantly creeping segment of a subduction zone generate a great (M  > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (≤0.3 m) to perturb the onshore geologic record. |
format |
Text |
author |
Witter, Robert C. Briggs, Richard W. Engelhart, Simon E. Gelfenbaum, Guy Koehler, Richard D. Barnhart, William D. |
spellingShingle |
Witter, Robert C. Briggs, Richard W. Engelhart, Simon E. Gelfenbaum, Guy Koehler, Richard D. Barnhart, William D. Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska |
author_facet |
Witter, Robert C. Briggs, Richard W. Engelhart, Simon E. Gelfenbaum, Guy Koehler, Richard D. Barnhart, William D. |
author_sort |
Witter, Robert C. |
title |
Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska |
title_short |
Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska |
title_full |
Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska |
title_fullStr |
Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska |
title_full_unstemmed |
Little Late Holocene Strain Accumulation and Release on the Aleutian Megathrust Below the Shumagin Islands, Alaska |
title_sort |
little late holocene strain accumulation and release on the aleutian megathrust below the shumagin islands, alaska |
publisher |
DigitalCommons@URI |
publishDate |
2014 |
url |
https://digitalcommons.uri.edu/geo_facpubs/7 https://doi.org/10.1002/2014GL059393 https://digitalcommons.uri.edu/context/geo_facpubs/article/1006/viewcontent/Witter_et_al_2014_Geophysical_Research_Letters.pdf |
genre |
glacier Alaska |
genre_facet |
glacier Alaska |
op_source |
Geosciences Faculty Publications |
op_relation |
https://digitalcommons.uri.edu/geo_facpubs/7 doi:10.1002/2014GL059393 https://digitalcommons.uri.edu/context/geo_facpubs/article/1006/viewcontent/Witter_et_al_2014_Geophysical_Research_Letters.pdf |
op_doi |
https://doi.org/10.1002/2014GL059393 |
container_title |
Geophysical Research Letters |
container_volume |
41 |
container_issue |
7 |
container_start_page |
2359 |
op_container_end_page |
2367 |
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1810444958982733824 |