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Shear wave birefringence in dilating granite
Author(s) -
Bonner B. P.
Publication year - 1974
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/gl001i005p00217
Subject(s) - dilatant , birefringence , shear (geology) , geology , anisotropy , shear waves , seismology , geotechnical engineering , principal stress , shear stress , materials science , optics , composite material , petrology , physics
Laboratory observations of ultrasonic shear waves indicate splitting along the direction of minimum principal stress of ∼11% for confined (20 MPa) and ∼16% for unconfined specimens of Westerly granite loaded in uniaxial stress. Dilatant strains increase birefringence except at > 80‐90% of the ultimate strength, when processes related to shear failure apparently become important. If seismic birefringence observed in the field can be related to anisotropic dilatant strains, these laboratory measurements of precursory velocity changes should prove useful in predicting earthquakes.