Detecting seismic anisotropy above the 410 km discontinuity using reflection coefficients of underside reflections

Morvarid Saki*, Christine Thomas, Sébastien Merkel, James Wookey

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

3 Citations (Scopus)
185 Downloads (Pure)

Abstract

We investigate the effect of various types of deformation mechanisms on the reflection coefficients of P and S waves underside reflections off the 410 km discontinuity, to develop a diagnostic tool to detect the style of deformation at boundary layers. We calculate the reflection coefficient for P and SH underside reflections using velocity perturbations resulting from aligned minerals above the 410 km discontinuity for different deformation scenarios. The results show that in the case of an anisotropic olivine layer above an isotropic wadsleyite layer, the P wave reflection coefficient amplitudes are only slightly influenced by the joint effect of angle of incidence and the strength of imposed deformation, without any polarity reversal and for all deformation styles. For the SH wave underside reflections the incidence angle for which a polarity reversal occurs, changes with distance for all scenarios and in addition changes with azimuth for shear deformation scenarios. These differences in amplitude and polarity patterns of reflection coefficients of different deformation geometries, especially for S wave at shorter distances potentially provide a possibility to distinguish between different styles of deformation at a boundary layer. We also show a first test using currently available elastic constants of anisotropic wadsleyite beneath anisotropic olivine.

Original languageEnglish
Pages (from-to)170-183
Number of pages14
JournalPhysics of the Earth and Planetary Interiors
Volume274
Early online date5 Dec 2017
DOIs
Publication statusPublished - Jan 2018

Keywords

  • 410 km seismic discontinuity
  • Anisotropy
  • Deformation style
  • Reflection coefficient
  • Underside reflections

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