Electric potential changes prior to shear fracture in dry and saturated rocks

Electric potential changes before shear rupture were measured using Darley Dale sandstone (quartz‐rich) and Icelandic basalt (quartz‐free) on both dry specimens and in the presence of pore fluid. We find that electric potential changed markedly just prior to dynamic rupture in dry and saturated sand...

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Bibliographic Details
Published in:Geophysical research letters 1998-05, Vol.25 (10), p.1577-1580
Main Authors: Yoshida, Shingo, Clint, Oswald C., Sammonds, Peter R.
Format: Article
Language:English
Subjects:
Earth sciences
Earth, ocean, space
Earthquakes, seismology
Exact sciences and technology
Geophysics: general, magnetic, electric and thermic methods and properties
Internal geophysics
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Summary:Electric potential changes before shear rupture were measured using Darley Dale sandstone (quartz‐rich) and Icelandic basalt (quartz‐free) on both dry specimens and in the presence of pore fluid. We find that electric potential changed markedly just prior to dynamic rupture in dry and saturated sandstones and saturated basalt but we did not detect precursory signals in dry basalt. The absence of signals in dry basalt provides strong evidence that the piezoelectric effect and electrokinetic effect are dominant sources for precursory signals. Moreover we find that the amplitude of the precursory signals due to electrokinetic effect in saturated sandstone were as large as the coseismic signals. We propose that this signal is caused by accelerating evolution of dilatancy as cracks grow in the rock before rupture, resulting in water flow into the dilatant region with an electric current produced concurrently.
ISSN:0094-8276
1944-8007
DOI:10.1029/98GL01222