HR: 1340h
AN: T33C-1494 [Abstracts]
TI: Displacement-Length Scaling Relations for Geologic Structural Discontinuities and Implications for Near-Tip Processes
AU: * Schultz, R
EM: schultz@mines.unr.edu
AF: University of Nevada, Geomechanics-Rock Fracture Group, Department of Geological
Sciences and Engineering, Reno, NV 89557, United States
AU: Soliva, R
EM: roger.soliva@gm.univ-montp2.fr
AF: Universite Montpellier II, Departement des Sciences de la Terre et de lEnvironnement,
Montpellier, 34000, France
AU: Fossen, H
EM: Haakon.Fossen@geo.uib.no
AF: University of Bergen, Department of Earth Science, Bergen, N-5007, Norway
AU: Okubo, C H
EM: chriso@lpl.arizona.edu
AF: The University of Arizona, Lunar and Planetary Laboratory, 1541 East University Boulevard,
Tucson, AZ 85721, United States
AU: Reeves, D M
EM: mreeves@dri.edu
AF: Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, United States
AB:
Displacement-length ( D-L) scaling relations for faults and other common geologic structures provide a
window into the mechanics of brittle strain localization. We present and synthesize the displacement-length data
for the various types of geologic structural discontinuities, including faults, joints, veins, igneous dikes,
deformation bands, and compaction bands. Neglecting the influence of short-range mechanical interaction and
other effects, the scaling relations of geologic structural discontinuities define two groups. The first group, having
a slope of n = 1 and therefore a linear dependence of maximum displacement and discontinuity length (
Dmax = γ L), comprises faults and shear deformation bands. These shearing-mode
structures grow under conditions of constant driving stress, such as shear stress drop, with the magnitude of
near-tip stress on the same order as the rock's yield strength in shear. The second group, having a slope of n
= 0.5 and therefore a square-root dependence of maximum displacement and discontinuity length (
Dmax = α L0.5), comprises hydrothermal veins, igneous dikes, cataclastic
(compactional/shear) deformation bands, and compaction bands. These opening- and closing-mode structures
grow under conditions of constant fracture toughness, implying driving stresses that scale inversely with L
and significant amplification of near-tip stress within a zone of small-scale yielding about the discontinuity tip.
Scaling exponents of n = 1 imply that rock shear strengths are much less than the tensile strength. On the
other hand, grain cracking, and thus control of propagation by the mode-I fracture toughness, appear responsible
for scaling with n = 0.5.
UR: http://mines.unr.edu/geo-eng/schultz
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8010 Fractures and faults
DE: 8020 Mechanics, theory, and modeling
DE: 8164 Stresses: crust and lithosphere
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting