Anisotropic upper-mantle stratigraphy and architecture of the Slave craton
Anisotropic upper-mantle stratigraphy and architecture of the Slave craton
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作者：
M. Bostock
地球的物理性质表现出以放射状为主的结构，这是成分分异、等化学相变和流变性分层的结果。流变性分层可能是使用常规地震学技术研究最困难的，因为这一特性的地震表现--弹性各向异性--可能非常接近于各向同性非均质性的影响。尽管如此，对地球流变结构的更好表征有望为板块动力学和大陆演化等过程提供重要的见解。在这里，我提出了一种利用远震P波的尾波有效地描述各向异性上地幔结构中急剧转变的方法。对来自奴隶克拉通的地震记录的应用表明，地层学很发达，至少部分各向异性，主要边界出现在标称深度75、135和195 公里处。这些不连续面的几何形状和尖锐程度表明是构造成因，可能涉及到浅层俯冲。
The Earth's physical properties show a dominantly radial structure which is the result of compositional differentiation, isochemical phase changes and rheological layering. Rheological layering is perhaps the most difficult to investigate using conventional seismological techniques because the seismic manifestation of this property, elastic anisotropy, may closely mimic the effects of isotropic heterogeneity. Nonetheless, an improved characterization of Earth's rheological structure promises important insights into such processes as plate dynamics and continental evolution. Here, I present a methodology for effectively characterizing sharp transitions in anisotropic, upper-mantle structure using the coda of teleseismic P-waves. Application to seismograms from the Slave craton reveals a well-developed stratigraphy, at least in part anisotropic, with major boundaries occurring at nominal depths of 75, 135 and 195 km. The geometry and sharpness of these discontinuities suggest a structural origin, perhaps involving shallow subduction.