Stream channel offset and Late Holocene slip rate of the San Andreas fault at the Van Matre Ranch site, Carrizo Plain, California

Gabriela R. Noriega, Ramon Arrowsmith, Lisa B. Grant, Jeri J. Young

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Sets of well-preserved channels offset across the San Andreas fault (SAF) at the Van Matre Ranch (VMR) site in the northwestern Elkhorn Hills area of the Carrizo Plain offer the opportunity to measure slip rate and examine geomorphic development of the channels. The fault zone and offset channels were exposed by excavation in one fault-perpendicular and five fault-parallel trenches. The geomorphology and stratigraphy in the channels reveal a record of filling by fluvial sedimentation, lateral colluviation, and pedogenesis. The buried thalweg of the currently active channel is offset 24.± 1 m, while the geomorphic channel is offset approximately 27.6 ± 1 m. Seventeen samples were collected from channel margin deposits for 14C dating. An OxCal model of the radiocarbon dates with stratigraphic control suggests that the oldest date for channel incision was ∼A.D. 1160. Minimum and maximum slip rates ranging from 29.3 to 35.6 mm/yr are derived from different assumptions about the timing of channel incision and offset. The resulting slip rates at VMR agree well with the late-Holocene slip rate of 33.9 ± 2.9 mm/yr at Wallace Creek, approximately 18 km to the northwest, and imply that within measurement uncertainty the 30-37 mm/yr velocity gradient across the SAF from decadal timescale geodetic measurements is accommodated across the several-meter-wide SAF zone at VMR over the last millennium.

Original languageEnglish (US)
Pages (from-to)33-47
Number of pages15
JournalBulletin of the Seismological Society of America
Volume96
Issue number1
DOIs
StatePublished - Feb 2006

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San Andreas Fault
slip rate
stream channel
trucks
plains
slip
Holocene
Geomorphology
Stratigraphy
Sedimentation
Excavation
Deposits
fault zone
geomorphology
thalweg
plain
excavation
stratigraphy
pedogenesis
dating

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Stream channel offset and Late Holocene slip rate of the San Andreas fault at the Van Matre Ranch site, Carrizo Plain, California. / Noriega, Gabriela R.; Arrowsmith, Ramon; Grant, Lisa B.; Young, Jeri J.

In: Bulletin of the Seismological Society of America, Vol. 96, No. 1, 02.2006, p. 33-47.

Research output: Contribution to journalArticle

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