Mattesini Maurizio, Belonoshko Anatoly B, Buforn Elisa, Ramírez María, Simak Sergei I, Udías Agustín, Mao Ho-Kwang, Ahuja Rajeev
Departamento de Física de la Tierra, Astronomía y Astrofísica I, Universidad Complutense de Madrid, E-28040 Madrid, Spain.
Proc Natl Acad Sci U S A. 2010 May 25;107(21):9507-12. doi: 10.1073/pnas.1004856107. Epub 2010 May 10.
It has been shown that the Earth's inner core has an axisymmetric anisotropic structure with seismic waves traveling approximately 3% faster along polar paths than along equatorial directions. Hemispherical anisotropic patterns of the solid Earth's core are rather complex, and the commonly used hexagonal-close-packed iron phase might be insufficient to account for seismological observations. We show that the data we collected are in good agreement with the presence of two anisotropically specular east and west core hemispheres. The detected travel-time anomalies can only be disclosed by a lattice-preferred orientation of a body-centered-cubic iron aggregate, having a fraction of their [111] crystal axes parallel to the Earth's rotation axis. This is compelling evidence for the presence of a body-centered-cubic Fe phase at the top of the Earth's inner core.
研究表明，地球内核具有轴对称各向异性结构，地震波沿极地路径传播的速度比沿赤道方向快约3%。固体地球内核的半球各向异性模式相当复杂，常用的六方密排铁相可能不足以解释地震学观测结果。我们表明，我们收集的数据与存在两个各向异性镜面反射的东、西内核半球的情况高度吻合。检测到的走时异常只能通过体心立方铁聚集体的晶格择优取向来揭示，其[111]晶轴的一部分与地球自转轴平行。这是地球内核顶部存在体心立方铁相的有力证据。
