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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >On the anelastic contribution to the temperature dependence of lower mantle seismic velocities
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On the anelastic contribution to the temperature dependence of lower mantle seismic velocities

机译：下地幔地震速度对温度依赖性的非弹性贡献

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摘要

There is little agreement regarding the importance of anelastic contributions to the temperature dependence of seismic wave velocities. Some studies consider the anelastic contribution to be negligible, whereas others argue that it may be as important as the purely elastic contribution. In order to evaluate these claims, we review physically plausible models for mantle relaxation processes and construct a model of activation enthalpy based on solid state physics as well as on recent experimental results. We then deduce self-consistent 1-D Q profiles and evaluate the anelastic contribution to the temperature dependence of Vs and Vp. Physically plausible values of activation enthalpies yield anelastic contributions that increase with depth and account for at least 20% of the velocity temperature derivatives at 2600 km. We show that anelasticity may significantly moderate temperature variations in hot (slow velocity) zones. This suggests that inferred lateral changes in temperature, as well as arguments regarding the presence of chemical heterogeneity, and/or temperature induced phase transformations, are likely to be significantly affected by anelastic effects in the mantle. We also compute values of the dimensionless parameters Rs/p, R/s, and Rρ/s. We find that anelasticity can either increase or decrease Rs/p, but the magnitude of the correction, of the order of 15%, is smaller than the uncertainty in the elastic value. Anelasticity cannot change the sign of R/s and Rρ/s, but it can decrease their values by as much as 50%. However, given current uncertainties in seismic and mineral data, the effects of anelasticity on the dimensionless parameters do not bring any quantitative constraints on lateral variations of temperature, chemical composition and/or mineral phase.
机译：关于非弹性贡献对地震波速度的温度依赖性的重要性几乎没有共识。一些研究认为无弹性的贡献可以忽略不计，而另一些研究则认为它可能与纯弹性的贡献一样重要。为了评估这些说法，我们回顾了地幔松弛过程的物理合理模型，并基于固态物理学以及最近的实验结果构建了活化焓模型。然后，我们推导自洽的一维Q轮廓，并评估非弹性对Vs和Vp的温度依赖性的影响。激活焓的物理合理值会产生非弹性贡献，其随深度增加，并且在2600 km处至少占速度温度导数的20％。我们表明，无弹性可以显着缓和热（慢速）区域中的温度变化。这表明推断的温度横向变化以及有关化学非均质性和/或温度引起的相变的论点很可能会受到地幔中非弹性作用的显着影响。我们还计算无量纲参数Rs / p，R / s和Rρ/ s的值。我们发现，无弹性可以增加或减少Rs / p，但是校正幅度约为15％，小于弹性值的不确定性。弹性不能更改R / s和Rρ/ s的符号，但可以将其值降低多达50％。但是，考虑到地震和矿物数据的当前不确定性，无弹性对无量纲参数的影响不会对温度，化学成分和/或矿物相的横向变化带来任何定量限制。

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