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Variation of compressional velocities in simulated fault gouge under normal and direct shear stress
Author(s) -
Peselnick L.,
Dieterich J. H.,
Mjachkin V. I.,
Sobolev G. A.
Publication year - 1976
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl003i007p00369
Subject(s) - fault gouge , shearing (physics) , geology , shear (geology) , shear stress , stress (linguistics) , comminution , grain size , critical resolved shear stress , geotechnical engineering , fault plane , mineralogy , materials science , composite material , fault (geology) , shear rate , seismology , petrology , metallurgy , geomorphology , linguistics , philosophy , viscosity
An experimental method designed to measure ultrasonic velocities in simulated fault gouge subjected to normal and direct shearing stress yields these results. For a well‐compacted, unsorted, fine‐grained, dry granite gouge under constant normal stress, reversible changes in V p with shear stress are observed prior to stable sliding. V p decreases by as much as 9% with increasing shear stress for the conditions of these experiments. For layers of intact granite slabs subjected to constant normal stress, and whose interfaces are relatively free of gouge material, V p increases with increasing shear stress. The observed velocity changes in the granite gouge experiments are believed to be produced by reversible opening and closing of small cracks. For a gouge material consisting of moderately compacted, sorted, coarser‐grained, dry sand, irreversible changes in V p were observed. The predominant changes in V p for the sand gouge are believed to result from grain fracturing and from readjustment of grains to a denser state of aggregation with changes in the general stress.