LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA

Abstract One of the largest historical earthquakes in the U.S. Pacific Northwest occurred on December 15, 1872 near the south end of Lake Chelan. Lack of recognized surface deformation suggested that the earthquake occurred on a blind, perhaps deep, fault. New LiDAR data revealed a NW‐side‐up scarp...

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Main Authors: Brian L. Sherrod, Richard J. Blakely, Craig S. Weaver
Format: Article
Language:English
Published: Wiley 2021-08-01
Series:Geophysical Research Letters
Subjects:
Online Access:https://doi.org/10.1029/2021GL093318
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author Brian L. Sherrod
Richard J. Blakely
Craig S. Weaver
author_facet Brian L. Sherrod
Richard J. Blakely
Craig S. Weaver
author_sort Brian L. Sherrod
collection DOAJ
description Abstract One of the largest historical earthquakes in the U.S. Pacific Northwest occurred on December 15, 1872 near the south end of Lake Chelan. Lack of recognized surface deformation suggested that the earthquake occurred on a blind, perhaps deep, fault. New LiDAR data revealed a NW‐side‐up scarp along the north side of Spencer Canyon near Entiat, Washington. Landslides triggered during the earthquake impounded small ponds in Spencer Canyon; the larger of the two landslides obliterated a portion of the scarp. Tree‐ring counts show that the oldest trees on each landslide are 130 and 128 years old, and lend credence to the idea that the earthquake triggered the landslides. Trenches across the scarp exposed a NW‐dipping thrust fault offsetting young soils and Mesozoic bedrock. Radiocarbon and tree ring data shows that the last fault movement was between 1856 and 1873 CE, and was most likely during the 1872 CE earthquake.
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spelling doaj-art-ebee0655075c4887b7e9df571bb49b152025-08-20T02:18:54ZengWileyGeophysical Research Letters0094-82761944-80072021-08-014816n/an/a10.1029/2021GL093318LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USABrian L. Sherrod0Richard J. Blakely1Craig S. Weaver2Department of Earth and Space Sciences U.S. Geological Survey University of Washington Seattle WA USAEmeritus U.S. Geological Survey Moffett Field CA USADepartment of Earth and Space Sciences Emeritus U.S. Geological Survey University of Washington Seattle WA USAAbstract One of the largest historical earthquakes in the U.S. Pacific Northwest occurred on December 15, 1872 near the south end of Lake Chelan. Lack of recognized surface deformation suggested that the earthquake occurred on a blind, perhaps deep, fault. New LiDAR data revealed a NW‐side‐up scarp along the north side of Spencer Canyon near Entiat, Washington. Landslides triggered during the earthquake impounded small ponds in Spencer Canyon; the larger of the two landslides obliterated a portion of the scarp. Tree‐ring counts show that the oldest trees on each landslide are 130 and 128 years old, and lend credence to the idea that the earthquake triggered the landslides. Trenches across the scarp exposed a NW‐dipping thrust fault offsetting young soils and Mesozoic bedrock. Radiocarbon and tree ring data shows that the last fault movement was between 1856 and 1873 CE, and was most likely during the 1872 CE earthquake.https://doi.org/10.1029/2021GL093318paleoseismologyHoloceneearthquakePacific Northwest
spellingShingle Brian L. Sherrod
Richard J. Blakely
Craig S. Weaver
LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA
Geophysical Research Letters
paleoseismology
Holocene
earthquake
Pacific Northwest
title LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA
title_full LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA
title_fullStr LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA
title_full_unstemmed LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA
title_short LiDAR and Paleoseismology Solve Earthquake Mystery in the Pacific Northwest, USA
title_sort lidar and paleoseismology solve earthquake mystery in the pacific northwest usa
topic paleoseismology
Holocene
earthquake
Pacific Northwest
url https://doi.org/10.1029/2021GL093318
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