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Seismic and aseismic slip on the San Andreas Fault

Scholz, C. H. and Wyss, M. and Smith, S. W. (1969) Seismic and aseismic slip on the San Andreas Fault. Journal of Geophysical Research, 74 (8). pp. 2049-2069. ISSN 0148-0227. doi:10.1029/JB074i008p02049.

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Field and experimental evidence are combined to deduce the mechanism of slip on shallow continental transcurrent faults, such as the San Andreas in California. Several lines of evidence portray the central section of the San Andreas fault as a very smooth and flat surface, with a very low frictional strength in comparison to the breaking strength of intact rock. The Parkfield earthquake of June 27, 1966, and its aftershock and creep sequences are examined as a detailed example of fault slippage that includes both types, seismic and aseismic. It is shown from considerable number of field data that during the main shock a region from about 4 to 10 km in depth slipped approximately 30 cm. In response to this slippage, creep and aftershocks were generated. The creep and aftershocks are not directly interrelated, but they are microscopically identical processes of time‐dependent brittle friction occurring in parallel in different regions. The creep occurred by time‐dependent stable frictional sliding in the 4‐km‐thick surface layer; the aftershocks, by time‐dependent stick‐slip at the ends of the initial slipped zone. This model is in good agreement with laboratory results which show that slippage should occur by stable (aseismic) friction in the upper 4 km, by stick‐slip accompanied by earthquakes from about 4 to 12 km, and by stable sliding or plastic friction below 12 km on the fault. One feature not observed in the laboratory is the episodic nature of creep. These episodes can be predicted with an accuracy of about 1 week.

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Additional Information:© 1969 by the American Geophysical Union. Received November 7, 1968; revised December 27, 1968. Contribution 1564, Division of Geological Sciences, California Institute of Technology, Pasadena, California. We would like to thank Jerry P. Eaton of the U.S. Geological Survey for supplying us with data from the Gold Hill seismographic station and for allowing us the use of his data on aftershock locations prior to publication. J. Brune, J. Byerlee, W. F. Brace, and K. Aki also are thanked for the use of their manuscripts prior to publication. We also thank Jack Oliver, Clarence Allen, Lynn Sykes, and Peter Molnar for reviewing the manuscript. This research was supported by the National Science Foundation under grant GA 1087 (Earthquake Mechanisms).
Group:Seismological Laboratory
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NSFGA 1087
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Caltech Division of Geological Sciences1564
Issue or Number:8
Record Number:CaltechAUTHORS:20190912-092334290
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Official Citation:Scholz, C. H., Wyss, M., and Smith, S. W. (1969), Seismic and aseismic slip on the San Andreas Fault, J. Geophys. Res., 74(8), 2049–2069, doi:10.1029/JB074i008p02049
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98603
Deposited By: Tony Diaz
Deposited On:12 Sep 2019 17:26
Last Modified:16 Nov 2021 17:40

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