Dislocation damping and anisotropic seismic wave attenuation in earth's upper mantle
Date
2012
Authors
Farla, Robert
Jackson, Ian
Fitz Gerald, John
Faul, Ulrich H
Zimmerman, M
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American Association for the Advancement of Science
Abstract
Crystal defects form during tectonic deformation and are reactivated by the shear stress associated with passing seismic waves. Although these defects, known as dislocations, potentially contribute to the attenuation of seismic waves in Earth's upper mantle, evidence for dislocation damping from laboratory studies has been circumstantial. We experimentally determined the shear modulus and associated strain-energy dissipation in pre-deformed synthetic olivine aggregates under high pressures and temperatures. Enhanced high-temperature background dissipation occurred in specimens pre-deformed by dislocation creep in either compression or torsion, the enhancement being greater for prior deformation in torsion. These observations suggest the possibility of anisotropic attenuation in relatively coarse-grained rocks where olivine is or was deformed at relatively high stress by dislocation creep in Earth's upper mantle.
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Keywords: damping; deformation mechanism; dislocation; high pressure; high temperature; olivine; seismic wave; shear stress; tectonic setting; upper mantle; wave attenuation; anisotropy; article; attenuation; compression; dislocation; geology; laboratory; noise red
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Science
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Journal article
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Restricted until
2037-12-31
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