The Catfish Lake Scarp, Allyn, Washington: Preliminary field data and implications for earthquake hazards posed by the Tacoma fault

Brian L. Sherrod; Alan R. Nelson; Harvey M. Kelsey; Thomas M. Brocher; Richard J. Blakely; Craig S. Weaver; Nancy K. Rountree; B. Susan Rhea; Bernard S. Jackson

doi:10.3133/ofr03455

The Catfish Lake Scarp, Allyn, Washington: Preliminary field data and implications for earthquake hazards posed by the Tacoma fault

Open-File Report 2003-455

By: Brian L. Sherrod, Alan R. Nelson, Harvey M. Kelsey, Thomas M. Brocher, Richard J. Blakely, Craig S. Weaver, Nancy K. Rountree, B. Susan Rhea, and Bernard S. Jackson

https://doi.org/10.3133/ofr03455

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Abstract

The Tacoma fault bounds gravity and aeromagnetic anomalies for 50 km across central Puget lowland from Tacoma to western Kitsap County. Tomography implies at least 6 km of post-Eocene uplift to the north of the fault relative to basinal sedimentary rocks to the south. Coastlines north of the Tacoma fault rose about 1100 years ago during a large earthquake. Abrupt uplift up to several meters caused tidal flats at Lynch Cove, North Bay, and Burley Lagoon to turn into forested wetlands and freshwater marshes. South of the fault at Wollochet Bay, Douglas-fir forests sank into the intertidal zone and changed into saltmarsh. Liquefaction features found beneath the marsh at Burley Lagoon point to strong ground shaking at the time of uplift. Recent lidar maps of the area southwest of Allyn, Washington revealed a 4 km long scarp, or two closely spaced en-echelon scarps, which correspond closely to the Tacoma fault gravity and aeromagnetic anomalies. The scarp, named the Catfish Lake scarp, is north-side-up, trends east-west, and clearly displace striae left by a Vashon-age glacier. A trench across the scarp exposed evidence for postglacial folding and reverse slip. No organic material for radiocarbon dating was recovered from the trench. However, relationships in the trench suggest that the folding and faulting is postglacial in age.

Suggested Citation

Sherrod, B.L., Nelson, A.R., Kelsey, H.M., Brocher, T.M., Blakely, R.J., Weaver, C.S., Rountree, N.K., Rhea, B.S., and Jackson, B.S., 2004, The Catfish Lake Scarp, Allyn, Washington: Preliminary field data and implications for earthquake hazards posed by the Tacoma fault (Version 1.0): U.S. Geological Survey Open-File Report 2003-455, Report: iii, 11 p.; 1 Sheet: 36.00 x 36.00 inches, https://doi.org/10.3133/ofr03455.

ISSN: 2331-1258 (online)

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Additional publication details
Publication type	Report
Publication Subtype	USGS Numbered Series
Title	The Catfish Lake Scarp, Allyn, Washington: Preliminary field data and implications for earthquake hazards posed by the Tacoma fault
Series title	Open-File Report
Series number	2003-455
DOI	10.3133/ofr03455
Edition	Version 1.0
Year Published	2004
Language	English
Publisher	U.S. Geological Survey
Contributing office(s)	Earthquake Science Center, Geologic Hazards Science Center, Geology, Minerals, Energy, and Geophysics Science Center
Description	Report: iii, 11 p.; 1 Sheet: 36.00 x 36.00 inches
Country	United States
State	Washington
City	Allyn
Other Geospatial	Catfish Lake scarp