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Summary of coastal geologic evidence for past great earthquakes at the Cascadia subduction zone

Brian F. Atwater, Alan R. Nelson, John J. Clague, Gary A. Carver, David K. Yamaguchi, Peter T. Bobrowsky, Joanne Bourgeois, Mark E. Darienzo, Wendy C. Grant, Eileen Hemphill-Haley, Harvey M. Kelsey, Gordon C. Jacoby, Stuart P. Nishenko, Stephen P. Palmer, Curt D. Peterson and Mary Ann Reinhart
Summary of coastal geologic evidence for past great earthquakes at the Cascadia subduction zone
Earthquake Spectra (February 1995) 11 (1): 1-18


Earthquakes in the past few thousand years have left signs of land-level change, tsunamis, and shaking along the Pacific coast at the Cascadia subduction zone. Sudden lowering of land accounts for many of the buried marsh and forest soils at estuaries between southern British Columbia and northern California. Sand layers on some of these soils imply that tsunamis were triggered by some of the events that lowered the land. Liquefaction features show that inland shaking accompanied sudden coastal subsidence at the Washington-Oregon border about 300 years ago. The combined evidence for subsidence, tsunamis, and shaking shows that earthquakes of magnitude 8 or larger have occurred on the boundary between the overriding North America plate and the downgoing Juan de Fuca and Gorda plates. Intervals between the earthquakes are poorly known because of uncertainties about the number and ages of the earthquakes. Current estimates for individual intervals at specific coastal sites range from a few centuries to about one thousand years.

ISSN: 8755-2930
EISSN: 1944-8201
Serial Title: Earthquake Spectra
Serial Volume: 11
Serial Issue: 1
Title: Summary of coastal geologic evidence for past great earthquakes at the Cascadia subduction zone
Affiliation: U. S. Geological Survey, Seattle, WA, United States
Pages: 1-18
Published: 199502
Text Language: English
Publisher: Earthquake Engineering Research Institute, Berkeley, CA, United States
References: 38
Accession Number: 1995-068062
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
Secondary Affiliation: Geological Survey of Canada, CAN, CanadaHumboldt State University, USA, United StatesForestry and Forest Products Research Institute, JPN, JapanMinistry of Energy, Mines, and Petroleum Resources, CAN, CanadaUniversity of Washington, USA, United StatesPortland State University, USA, United StatesLamont-Doherty Earth Observatory, USA, United StatesWashington Division of Geology and Earth Resources, USA, United StatesGeoEngineers, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 199524
Program Name: USGSOPNon-USGS publications with USGS authors
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