Seismic anisotropy of the D″ layer induced by (001) deformation of post-perovskite

Xiang Wu; Jung-Fu Lin; Pamela Kaercher; Zhu Mao; Jin Liu; Hans-Rudolf Wenk; Vitali B Prakapenka

doi:10.1038/ncomms14669

Seismic anisotropy of the D″ layer induced by (001) deformation of post-perovskite

Nat Commun. 2017 Apr 18:8:14669. doi: 10.1038/ncomms14669.

Authors

Xiang Wu¹, Jung-Fu Lin², Pamela Kaercher³, Zhu Mao⁴, Jin Liu², Hans-Rudolf Wenk⁵, Vitali B Prakapenka⁶

Affiliations

¹ State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China.
² Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin, Texas 78712, USA.
³ Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool L69 3GP, UK.
⁴ School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
⁵ Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA.
⁶ Center for Advanced Radiation Sources, The University of Chicago, Chicago, Illinois 60637, USA.

Abstract

Crystallographic preferred orientation (CPO) of post-perovskite (Mg,Fe)SiO₃ (pPv) has been believed to be one potential source of the seismic anisotropic layer at the bottom of the lower mantle (D″ layer). However, the natural CPO of pPv remains ambiguous in the D″ layer. Here we have carried out the deformation experiments of pPv-(Mg_0.75,Fe_0.25)SiO₃ using synchrotron radial X-ray diffraction in a membrane-driven laser-heated diamond anvil cell from 135 GPa and 2,500 K to 154 GPa and 3,000 K. Our results show that the intrinsic texture of pPv-(Mg_0.75,Fe_0.25)SiO₃ should be (001) at realistic P-T conditions of the D″ layer, which can produce a shear wave splitting anisotropy of ∼3.7% with V_SH>V_SV. Considering the combined effect of both pPv and ferropericlase, we suggest that 50% or less of deformation is sufficient to explain the origin of the shear wave anisotropy observed seismically in the D″ layer beneath the circum-Pacific rim.

Publication types

Research Support, Non-U.S. Gov't