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Electric potential changes prior to shear fracture in dry and saturated rocks
Author(s) -
Yoshida Shingo,
Clint Oswald C.,
Sammonds Peter R.
Publication year - 1998
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 - 10.1029/98gl01222
Subject(s) - dilatant , geology , basalt , quartz , electrokinetic phenomena , shear (geology) , mineralogy , amplitude , petrology , geotechnical engineering , geochemistry , materials science , paleontology , physics , quantum mechanics , nanotechnology
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.