Anisotropy: a pervasive feature of fault zones? |
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| Authors: | Russ Evans |
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| Institution: | Institute of Geological Sciences, Murchison House, West Mains Road, Edinburgh EH9 3LA, Scotland |
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| Abstract: | Summary. Current models of the structure of an active fault zone recognize two important subdivisions – an upper zone, extending to mid-crustal depths, in which processes associated with brittle fracture and friction dominate the fault behaviour, and a lower zone, extending into the mantle, within which stresses may be relieved by ductile flow. Anisotropy directly or indirectly induced by stress might occur throughout the fault zone, especially if caused by some form of stress-induced crack alignment. Dilatancy associated with high stresses is likely to be a very localized phenomenon in the vicinity of high strength regions (asperities), but alignments caused by subcritical crack growth at low stress and strain rate ( extensive-dilatancy anisotropy ) could give rise to anisotropy throughout the fault region. |
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