Open AccessAnisotropy: a pervasive feature of fault zones?
Author(s) -
Evans Russ
Publication year - 1984
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1984.tb05031.x
Subject(s) - anisotropy , geology , feature (linguistics) , seismology , fault (geology) , seismic anisotropy , geophysics , physics , mantle (geology) , optics , philosophy , linguistics
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.