Evaluating post-perovskite as a cause of D" anisotropy in regions of palaeosubduction

Andy J Nowacki, Andrew M Walker, James M Wookey, J M Kendall

Research output: Contribution to journalArticle (Academic Journal)

24 Citations (Scopus)

Abstract

Seismic anisotropy in the Earth's lowermost mantle (D″) is often attributed to the alignment of MgSiO3 post-perovskite (ppv) by the movement of dislocations in response to mantle flow. However, ppv's plastic yield surface is not known; nor do we know if this is the main deformation mechanism. We make use of a heterogeneous, generally anisotropic model of elasticity in D″derived from a 3-D model of mantle flow, which is obtained by inversion of geophysical observables. Unlike previous approaches, completely general, 3-D flow and full anisotropy are permitted, yielding more information to compare with observations than has been possible before. We model observations of anisotropy in D″by calculating the shear wave splitting predicted in ScS waves for a series of models of ppv plasticity. We find that observations in regions of the lowermost mantle beneath subduction zones are best fit by a model which accommodates slip on (010). Our results show that, within one standard deviation, slip on (010)-or a mechanism giving the same style of anisotropy-explains D″anisotropy beneath these regions.

Original languageEnglish
Pages (from-to)1085-1090
Number of pages6
JournalGeophysical Journal International
Volume192
Issue number3
Early online date10 Dec 2012
DOIs
Publication statusPublished - Mar 2013

Keywords

  • LOWERMOST-MANTLE
  • CONSTRAINTS
  • SEISMIC ANISOTROPY
  • DEFORMATION
  • BENEATH
  • Seismic anisotropy
  • EARTHS LOWER MANTLE
  • MGSIO3
  • Creep and deformation
  • Dynamics of lithosphere and mantle
  • PHASE-TRANSITION
  • MINERAL PHYSICS
  • Rheology: mantle
  • SHEAR
  • Mantle processes

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