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Fault orientations in extensional and conjugate strike-slip environments and their implications

Geology

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Abstract

Seismically active conjugate strike-slip faults in California and Japan typically have mutually orthogonal right- and left-lateral fault planes. Normal-fault dips at earthquake nucleation depths are concentrated between 40?? and 50??. The observed orientations and their strong clustering are surprising, because conventional faulting theory suggests fault initiation with conjugate 60?? and 120?? intersecting planes and 60?? normal-fault dip or fault reactivation with a broad range of permitted orientations. The observations place new constraints on the mechanics of fault initiation, rotation, and evolutionary development. We speculate that the data could be explained by fault rotation into the observed orientations and deactivation for greater rotation or by formation of localized shear zones beneath the brittle-ductile transition in Earth's crust. Initiation as weak frictional faults seems unlikely. -Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Fault orientations in extensional and conjugate strike-slip environments and their implications
Series title:
Geology
Volume
19
Issue:
11
Year Published:
1991
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
1116
Last page:
1120
Number of Pages:
5