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Nearly frictionless faulting by unclamping in long-term interaction models

Geology

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DOI: 10.1130/0091-7613(2002)030<1063:NFFBUI>2.0.CO;2

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Abstract

In defiance of direct rock-friction observations, some transform faults appear to slide with little resistance. In this paper finite element models are used to show how strain energy is minimized by interacting faults that can cause long-term reduction in fault-normal stresses (unclamping). A model fault contained within a sheared elastic medium concentrates stress at its end points with increasing slip. If accommodating structures free up the ends, then the fault responds by rotating, lengthening, and unclamping. This concept is illustrated by a comparison between simple strike-slip faulting and a mid-ocean-ridge model with the same total transform length; calculations show that the more complex system unclapms the transforms and operates at lower energy. In another example, the overlapping San Andreas fault system in the San Francisco Bay region is modeled; this system is complicated by junctions and stepovers. A finite element model indicates that the normal stress along parts of the faults could be reduced to hydrostatic levels after ???60-100 k.y. of system-wide slip. If this process occurs in the earth, then parts of major transform fault zones could appear nearly frictionless.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Nearly frictionless faulting by unclamping in long-term interaction models
Series title:
Geology
DOI:
10.1130/0091-7613(2002)030<1063:NFFBUI>2.0.CO;2
Volume
30
Issue:
12
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1063
Last page:
1066
Number of Pages:
4