Origin of seismic anisotropy in the D" layer inferred from shear deformation experiments on post-perovskite phase
Origin of seismic anisotropy in the D" layer inferred from shear deformation experiments on post-perovskite phase
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DOI：
10.1016/j.epsl.2006.10.004
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发表时间：
2006-12-15
影响因子：
5.3
通讯作者：
Yoneda, Akira
中科院分区：
文献类型：
--
作者：
Yamazaki, Daisuke;Yoshino, Takashi;Yoneda, Akira
地震各向异性是地球D”层的重要特征之一，被认为是由组成材料的晶格优先取向（LPO）或非均质材料（如熔体和包裹体）的形状优先取向（SPO）引起的。最近的实验和理论研究强烈表明，D”层主要由MgSiO3后钙钛矿相和铁镁长石组成。为了了解D”层的各向异性，我们对多晶caro3 （MgSiO3的类似物）进行了一系列高温高压下的简单剪切变形实验，并测量了后钙钛矿相的LPO。变形后钙钛矿相的晶体取向分析显示出较强的LPOs，主要滑移体系为[100]（010）。考虑后钙钛矿和铁方长石lpo影响的弹性波速计算结果显示，水平剪切平面的方位角和极化各向异性，水平极化s波速度明显快于垂直极化s波速度。因此，D”层观测到的地震各向异性可以用后钙钛矿和铁镁长石混合物的LPO来合理解释，其中LPO可能是地幔对流产生的水平剪切流的结果。(c) 2006 Elsevier B.V.版权所有
Seismic anisotropy is one of the significant features in the D" layer of the Earth and is thought to be derived from the lattice preferred orientation (LPO) of constituent materials or shape preferred orientation (SPO) of heterogeneous materials such as melt and inclusions. Recent experimental and theoretical studies strongly suggest that the D" layer consists mainly of a MgSiO3 Postperovskite phase together with ferro-periclase. To understand the anisotropy in the D" layer, we have conducted a series of simple shear deformation experiments at high temperature and pressure on polycrystalline CaIrO3 as an analogue of MgSiO3 and measured the LPO of the post-perovskite phase. Crystallographic orientation analysis of the deformed post-perovskite phase showed strong LPOs with the dominant slip system being [100](010). Calculation of the elastic wave velocities considering the effect of LPOs of post-perovskite and ferro-periclase showed as azimuthal and polarization anisotropies in the horizontal shear plane where the velocity of horizontally polarized S-wave is considerably faster than that of vertically polarized S-wave. Thus, the seismic anisotropy observed in the D" layer can be reasonably explained by the LPO of the mixture of post-perovskite and ferro-periclase, where the LPO may result from the horizontal shear flow generated by the mantle convection. (c) 2006 Elsevier B.V. All rights reserved.