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Long-term slip rate of the southern San Andreas Fault from ^(10)Be-^(26)Al surface exposure dating of an offset alluvial fan

van der Woerd, Jérôme and Klinger, Yann and Sieh, Kerry and Tapponnier, Paul and Ryerson, Frederick J. and Mériaux, Anne-Sophie (2006) Long-term slip rate of the southern San Andreas Fault from ^(10)Be-^(26)Al surface exposure dating of an offset alluvial fan. Journal of Geophysical Research B, 111 (B4). Art. No. B04407. ISSN 0148-0227. doi:10.1029/2004JB003559.

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We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using ^(10)Be and ^(26)Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allows precise determination of piercing points across the fault zone that are used to measure an offset of 565 ± 80 m. A total of 26 quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yields an age of 35.5 ± 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 ± 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0–14 ka) and short-term geodetic estimates for this part of the San Andreas Fault, implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 kyr. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip rates over different timescales.

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Sieh, Kerry0000-0002-7311-2447
Additional Information:© 2006 American Geophysical Union. Received 30 November 2004; revised 21 December 2005; accepted 12 January 2006; published 15 April 2006. We like to thank Granite Corporation for allowing unlimited access to the fans and especially to Lola Green and Lilburn Corporation for sharing topographic data. Tom Rockwell was kind enough to take one of us in his plane to fly over the Indio Hills. We thank S. Mitchell and B. Dorsey for their critical reviews and comments that improved the final version of the manuscript. We thank R. C. Finkel and M. W. Caffee at Lawrence Livermore National Laboratory for their help in analyzing the samples. The Lawrence Livermore National Laboratory (LLNL) group acknowledges support from the Laboratory Directed Research and Development Program at LLNL, operating under the auspices of the U.S. Department of Energy contract W-7405-Eng-48. This research was supported in part by the Gordon and Betty Moore Foundation. This is Caltech Tectonic Observatory contribution 9.
Group:Caltech Tectonics Observatory
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Department of EnergyW-7405-Eng-48
Subject Keywords:slip rate; cosmogenic dating; 10Be; San Andreas Fault; southern California
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Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory9
Issue or Number:B4
Record Number:CaltechAUTHORS:20101117-084033453
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Official Citation:van der Woerd, J., Y. Klinger, K. Sieh, P. Tapponnier, F. J. Ryerson, and A.-S. Mériaux (2006), Long-term slip rate of the southern San Andreas Fault from 10Be-26Al surface exposure dating of an offset alluvial fan, J. Geophys. Res., 111, B04407, doi:10.1029/2004JB003559
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20844
Deposited By: Tony Diaz
Deposited On:17 Nov 2010 18:53
Last Modified:09 Nov 2021 00:03

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