New Evidence on the State of Stress of the San Andreas Fault System

Contemporary in situ tectonic stress indicators along the San Andreas fault system in central California show northeast-directed horizontal compression that is nearly perpendicular to the strike of the fault. Such compression explains recent uplift of the Coast Ranges and the numerous active reverse...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1987-11, Vol.238 (4830), p.1105-1111
Main Authors: Zoback, Mark D., Zoback, Mary Lou, Mount, Van S., Suppe, John, Eaton, Jerry P., Healy, John H., Oppenheimer, David, Reasenberg, Paul, Jones, Lucile, Raleigh, C. Barry, Wong, Ivan G., Scotti, Oona, Wentworth, Carl
Format: Article
Language:English
Subjects:
California
Compressive stress
Earthquakes
Fault zones
Geology
Heat transfer
Plate tectonics
Seismological research
Shear stress
Stress fields
Stress measurement
Tectonics
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Summary:Contemporary in situ tectonic stress indicators along the San Andreas fault system in central California show northeast-directed horizontal compression that is nearly perpendicular to the strike of the fault. Such compression explains recent uplift of the Coast Ranges and the numerous active reverse faults and folds that trend nearly parallel to the San Andreas and that are otherwise unexplainable in terms of strike-slip deformation. Fault-normal crustal compression in central California is proposed to result from the extremely low shear strength of the San Andreas and the slightly convergent relative motion between the Pacific and North American plates. Preliminary in situ stress data from the Cajon Pass scientific drill hole (located 3.6 kilometers northeast of the San Andreas in southern California near San Bernardino, California) are also consistent with a weak fault, as they show no right-lateral shear stress at $\sim $2-kilometer depth on planes parallel to the San Andreas fault.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.238.4830.1105