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SUMMARY:Evolution of Anisotropy in Olivine Polycrystals - Neil Ribe (CNRS 
 (Centre national de la recherche scientifique)\; Université Paris Saclay)
DTSTART:20160415T123000Z
DTEND:20160415T133000Z
UID:TALK65511@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:Progressive deformation of upper mantle rocks via dislocation 
 creep causes their constituent crystals to take on a non-random orientatio
 n distribution (crystallographic preferred orientation or CPO) whose obser
 vable signatures include shear-wave splitting and azimuthal dependence of 
 surface wave speeds. Comparison of these signatures with mantle flow model
 s thus allows mantle dynamics to be unraveled on global and regional scale
 s. However\, existing self-consistent models of CPO evolution are computat
 ionally expensive when used in 3-D and/or time-dependent convection models
 . We propose a new method\, called ANPAR\, which is based on an analytical
  parameterization of the crystallographic spin predicted by the second-ord
 er (SO) self-consistent theory. Our parameterization runs &asymp\;2&ndash\
 ;6\\times 10^4&nbsp\;times faster than the SO model and fits its predictio
 ns for CPO and crystallographic spin with a variance reduction >99 per cen
 t. We illustrate the ANPAR model predictions fo r the deformation of olivi
 ne with three dominant slip systems\, (010)[100]\, (001)[100] and (010)[00
 1]\, for three uniform deformations (uniaxial compression\, pure shear and
  simple shear) and for a corner-flow model of a spreading mid-ocean ridge.
LOCATION:Seminar Room 1\, Newton Institute
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