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Compressive and tensile failure at high fluid pressure where preexisting fractures have cohesive strength, with application to the San Andreas fault

Journal of Geophysical Research B: Solid Earth

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Abstract

In thrusting and strike-slip situations, when the maximum principal horizontal stress S1 acts nearly normal to a fault (a misoriented fault, such as the San Andreas), pore-fluid pressure > the lithostatic load, Pf > Sv, is required to reactivate movement on that fault. Pf > Sv may be achieved without causing hydraulic tensile fracturing if (1) previously existing cracks have regained cohesive strength by chemical processes, (2) subcritical crack growth has been blunted, and (3) the least principal horizontal stress S3 nearly equals Sv. Where Pf > Sv has been attained within a misaligned fault, increasing the stress difference (S1 - S3) at constant Pf > Sv will not lead to shear failure, while a decrease in (S1 - S3) can lead to shear failure of that fault. However, where the cohesive strength of material in a broad misaligned fault zone is less than that of the surrounding intact rock, increasing (S1 - S3) while Pf > Sv can result in shear failure of fractures at near optimum angles to S1, but confined within this weak fault zone. If this faulting results in the local short-lived attainment of Pf > Sv (cataclastic deformation and frictional heating overcoming dilation) and a simultaneous decrease in (S1 - S3), this combination of effects can trigger movement along the main trace of the misaligned fault. When increasing Pf results in hydraulic failure, anisotropy in tensile strength or fracture toughness resulting from foliation within faults allows fractures to propagate along the planes of weakness rather than across the foliation perpendicular to S3.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Compressive and tensile failure at high fluid pressure where preexisting fractures have cohesive strength, with application to the San Andreas fault
Series title:
Journal of Geophysical Research B: Solid Earth
Volume
101
Issue:
B11
Year Published:
1996
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research B: Solid Earth
First page:
25499
Last page:
25509