HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Electronic Supplement Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Toké, N. A. Articles by Crosby, C. J. Search for Related Content GeoRef GeoRef Citation

Paleoseismic and Postseismic Observations of Surface Slip along the Parkfield Segment of the San Andreas Fault

¹ Department of Geological Sciences
Arizona State University
Box 871404
Tempe, Arizona 85287-1404
Nathan.toke{at}asu.edu
ramon.arrowsmith{at}asu.edu

Parkfield is considered a transitional segment along the San Andreas fault (SAF) between continuous fault creep to the northwest and segments to the southeast that last slipped in the great 1857 Fort Tejón earthquake. Historically, creep and recurring M 6.0 earthquakes have been observed at Parkfield, California, but the segment’s relevance in great SAF earthquakes has remained uncertain. This paleoseismic study of the central Parkfield segment provides a >2000-year record of tectonically deformed fluvial and sag stratigraphy. Two fault-perpendicular excavations across a pressure ridge and a sag pond 200 m north of Carr Hill exposed five primary fault zones displaying apparent vertical offsets, upward splaying clay shear bands, and warped stratigraphy. Four of five fault zones extended into the uppermost stratigraphy, suggesting recent surface offset and fault creep. Several antithetic fault splays and one primary fault zone displayed upward terminations, but strong indicators of large-magnitude earthquakes with meter-scale surface offset and rupture such as filled fissures and colluvial scarp deposits were not observed. The absence of evidence for large-magnitude earthquakes does not preclude the possibility of 1857-style earthquakes extending into the Parkfield segment. However, all deformation exposed within these trenches is consistent with repeated small ground rupture and fault creep. The 2004 M 6.0 Parkfield earthquake ruptured through the site and activated at least three of the five fault zones exposed in our excavations. Comparison between 2004 vertical offset and vertical offsets within the exposed stratigraphy suggests a recurrence interval between 8 and 188 years for M 6.0 earthquakes at Parkfield.

Online material: Supplemental unit descriptions, unanalyzed radiocarbon samples, and trench logs and photos.

This article has been cited by other articles:

				R. A. Harris and J R. Arrowsmith Introduction to the Special Issue on the 2004 Parkfield Earthquake and the Parkfield Earthquake Prediction Experiment Bulletin of the Seismological Society of America, September 1, 2006; 96(4B): S1 - S10. [Abstract] [Full Text] [PDF]

				M. J. Rymer, J. C. Tinsley III, J. A. Treiman, J R. Arrowsmith, K. B. Clahan, A. M. Rosinski, W. A. Bryant, H. A. Snyder, G. S. Fuis, N. A. Toke, et al. Surface Fault Slip Associated with the 2004 Parkfield, California, Earthquake Bulletin of the Seismological Society of America, September 1, 2006; 96(4B): S11 - S27. [Abstract] [Full Text] [PDF]

				N. A. Toke and J R. Arrowsmith Reassessment of a Slip Budget along the Parkfield Segment of the San Andreas Fault Bulletin of the Seismological Society of America, September 1, 2006; 96(4B): S339 - S348. [Abstract] [Full Text] [PDF]