Analytical parametrization of self-consistent polycrystal mechanics: Fast calculation of upper mantle anisotropy
Analytical parametrization of self-consistent polycrystal mechanics: Fast calculation of upper mantle anisotropy
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DOI：
10.1093/gji/ggv304
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发表时间：
2014-12
影响因子：
2.8
通讯作者：
N. Goulding;N. Ribe;O. Castelnau;A. Walker;J. Wookey
中科院分区：
文献类型：
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作者：
N. Goulding;N. Ribe;O. Castelnau;A. Walker;J. Wookey
位错蠕变导致上地幔岩石的渐进变形导致其组成晶体呈现非随机取向分布（晶体择优取向或 CPO），其可观察特征包括剪切波分裂和表面波速度的方位角依赖性。因此，将这些特征与地幔流模型进行比较，可以在全球和区域尺度上揭示地幔动力学。然而，现有的 CPO 演化自洽模型在用于 3D 和/或瞬态对流模型时计算成本较高。在这里，我们提出了一种称为 ANPAR 的新方法，它基于二阶 (SO) 自洽理论预测的晶体自旋的分析参数化。我们的参数化运行速度比 SO 模型快大约 2-6x10^4 倍，并且符合其对 CPO 和晶体自旋的预测，方差减少了 > 99%。我们举例说明了 ANPAR 模型对具有三种主要滑移系统（(010)[100]、(001)[100] 和 (010)[001] 的橄榄石变形的预测，对三种均匀变形（单轴压缩、纯剪切、简单剪切）以及扩展的洋中脊角流模型的预测。
Progressive deformation of upper mantle rocks via dislocation creep causes their constituent crystals to take on a non-random orientation distribution (crystallographic preferred orientation or CPO) whose observable signatures include shear-wave splitting and azimuthal dependence of surface wave speeds. Comparison of these signatures with mantle flow models thus allows mantle dynamics to be unraveled on global and regional scales. However, existing self-consistent models of CPO evolution are computationally expensive when used in 3-D and/or time-dependent convection models. Here we propose a new method, called ANPAR, which is based on an analytical parameterisation of the crystallographic spin predicted by the second-order (SO) self-consistent theory. Our parameterisation runs approximately 2-6x10^4 times faster than the SO model and fits its predictions for CPO and crystallographic spin with a variance reduction > 99%. We illustrate the ANPAR model predictions for the deformation of olivine with three dominant slip systems, (010)[100], (001)[100] and (010)[001], for three uniform deformations (uniaxial compression, pure shear, simple shear) and for a corner-flow model of a spreading mid-ocean ridge.