Implications of earthquake focal mechanisms for the frictional strength of the San Andreas fault system
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Published:January 01, 2001
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CiteCitation
John Townend, Mark D. Zoback, 2001. "Implications of earthquake focal mechanisms for the frictional strength of the San Andreas fault system", The Nature and Tectonic Significance of Fault Zone Weakening, R. E. Holdsworth, R. A. Strachan, J. F. Magloughlin, R. J. Knipe
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Abstract
Analysis of stress orientation data from earthquake focal plane mechanisms adjacent to the San Andreas fault in the San Francisco Bay area and throughout southern California indicates that the San Andreas fault has low frictional strength. In both regions, available stress orientation data indicate low levels of shear stress on planes parallel to the San Andreas fault. In the San Francisco Bay area, focal plane mechanisms from within 5 km of the San Andreas and Calaveras fault zones indicate a direction of maximum horizontal compression nearly orthogonal to both subvertical, right-lateral strikeslip faults, a result consistent with those obtained...
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Contents
The Nature and Tectonic Significance of Fault Zone Weakening

Many faults appears to form persistent zones of weakness that fundamentally influence the distribution, arichitecture and movement patterns of crustal-scale deformation and associated processes in both continental and oceanic regions. They act as conduits for the focused migration of economically important fluids and, as most seismicity is associated with active faults, they also constitute one of the most important global geological hazards.
This book brings together papers by an international group of Earth Scientists to discuss a broad range of topics centred upon the controls of fault weakening and the role of such faults during lithosphere deformation.
The book will be of interests to both academic and industrial Earth Scientists with an interest in geodynamics, structure at all scales, tectonics and the migration of petroleum and water.