INNER-CORE ANISOTROPY AND ROTATION
INNER-CORE ANISOTROPY AND ROTATION
复制标题
内核各向异性和旋转
DOI：
10.1146/annurev.earth.29.1.47
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发表时间：
2001
影响因子：
14.9
通讯作者：
J. Tromp
中科院分区：
文献类型：
--
作者：
J. Tromp
摘要本文综述了最近关于地球内核的研究。大的内核走时异常和核敏感自由振荡的异常分裂强烈表明内核是各向异性的。最初的模型涉及一个简单的、恒定的或深度相关的圆柱形各向异性，其水平小于几个百分点。最近的观测表明，它的东半球基本上是各向同性的，而西半球则是高度各向异性的，有迹象表明，它的顶部100公里可能是各向同性的。利用内核反射相的尾波可以推断出长度仅为几公里的强非均质性。因此，一幅复杂的地核三维图像开始浮现，尽管有人提出，这种复杂性的大部分可能是对起源于最下层地幔的信号的误解。地球动力学的数值模型表明，内核的旋转速度可能与地幔略有不同。最近基于走时和正常模式数据的地震学估计将内核的差旋转限制在每年小于0.2度。
■ Abstract This paper reviews recent research focused on the Earth’s inner core. Large inner-core traveltime anomalies and the anomalous splitting of core-sensitive free oscillations strongly suggest that the inner core is anisotropic. Initial models involved a simple, constant or depth-dependent cylindrical anisotropy at a level less than a few percent. Recent observations suggest that its eastern hemisphere is largely isotropic, whereas its western hemisphere is highly anisotropic, and there are indications that its top 100 km may be isotropic. The coda of inner-core reflected phases has been used to infer strong heterogeneities with a length scale of just a few kilometers. Thus, a complicated three-dimensional picture of the inner core is beginning to emerge, although it has been suggested that much of this complexity may be the misinterpretation of signals that have their origin in the lowermost mantle. Numerical models of the geodynamo suggest that the inner core may rotate at a slightly different rate than the mantle. Recent seismological estimates based upon traveltime and normal-mode data limit inner-core differential rotation to less thanC0.2 degrees per year.