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Strength of chrysotile-serpentinite gouge under hydrothermal conditions: Can it explain a weak San Andreas fault?

Geology

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Abstract

Chrysotile-bearing serpentinite is a constituent of the San Andreas fault zone in central and northern California. At room temperature, chrysotile gouge has a very low coefficient of friction (?? ??? 0.2), raising the possibility that under hydrothermal conditions ?? might be reduced sufficiently (to ???0.1) to explain the apparent weakness of the fault. To test this hypothesis, we measured the frictional strength of a pure chrysotile gouge at temperatures to 290??C and axial-shortening velocities as low as 0.001 ??m/s. As temperature increases to ???100??C, the strength of the chrysotile gouge decreases slightly at low velocities, but at temperatures ???200??C, it is substantially stronger and essentially independent of velocity at the lowest velocities tested. We estimate that pure chrysotile gouge at hydrostatic fluid pressure and appropriate temperatures would have shear strength averaged over a depth of 14 km of 50 MPa. Thus, on the sole basis of its strength, chrysotile cannot be the cause of a weak San Andreas fault. However, chrysotile may also contribute to low fault strength by forming mineral seals that promote the development of high fluid pressures.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Strength of chrysotile-serpentinite gouge under hydrothermal conditions: Can it explain a weak San Andreas fault?
Series title:
Geology
Volume
24
Issue:
11
Year Published:
1996
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
1041
Last page:
1044