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Open-File Report 2014–1002

Photomosaics and Event Evidence from the Frazier Mountain Paleoseismic Site, Trench 1, Cuts 1–4, San Andreas Fault, Southern California (2007–2009)

By Katherine M. Scharer, Tom E. Fumal, Ray J. Weldon, II, and Ashley R. Streig


The Frazier Mountain paleoseismic site is located at the northwest end of the Mojave section of the San Andreas Fault, in a small, closed depression at the base of Frazier Mountain near Tejon Pass, California (lat 34.8122° N., long 118.9034° W.). The site was known to contain a good record of earthquakes due to previous excavations by Lindvall and others (2002). This report provides data resulting from four nested excavations, or cuts, along trench 1 (T1) in 2007 and 2009 at the Frazier Mountain site. The four cuts were excavated progressively deeper and wider in an orientation perpendicular to the San Andreas Fault, exposing distal fan and marsh sediments deposited since ca. A.D. 1200. The results of the trenching show that earthquakes that ruptured the site have repeatedly produced a small depression or sag on the surface, which is subsequently infilled with sand and silt deposits. This report provides high-resolution photomosaics and logs for the T1 cuts, a detailed stratigraphic column for the deposits, and a table summarizing all of the evidence for ground rupturing paleoearthquakes logged in the trenches.

First posted February 26, 2014

For additional information, contact:
Contact Information, Menlo Park, Calif.
Office—Earthquake Science Center
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, CA 94025

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Suggested citation:

Scharer, K.M., Fumal, T.E., Weldon, R.J., II, and Streig, A.R., 2014, Photomosaics and event evidence from the Fazier Mountain paleoseismic site, trench 1, cuts 1–4, San Andreas Fault Zone, southern California (2007–2009): Open-File Report 2014–1002, 4 sheets, pamphlet, 23 p., various scales,

ISSN 2331-1258

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