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Mapping P-wave Azimuthal Anisotropy near the Core-Mantle Boundary using Novel Observations of Core-Diffracted waves PcSdiff

使用核心衍射波 PcSdiff 的新观测来绘制核心-地幔边界附近的 P 波方位各向异性

基本信息

批准号：
NE/T001372/1
负责人：
Teh-Ru Alex Song
金额：
$ 50.74万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT001372%2F1
关键词：
Mapping wave Azimuthal Anisotropy near

项目摘要

While the Earth's surface marks the boundary between the atmosphere and the solid earth, the core-mantle boundary (CMB) separates the solid mantle from the liquid core, modulating the loss of heat and driving the earth's dynamo and magnetic field.Constraining seismic anisotropy in the CMB region is challenging. Previous results on S wave anisotropy are subjected to some limitation in geographical sampling, azimuthal coverage or/and proper correction of upper mantle seismic anisotropy, which is not trivial. None of previous studies, neither in isolation or in combination, regional or global scale, has yielded any estimate of P-wave azimuthal anisotropy in the D'' layer. We do NOT know P wave anisotropy property of ultra-low velocity zones (ULVZs), large low-velocity provinces (LLVPs) or slab graveyards.We will use novel observations of core-diffracted PcSdiff wave in the radial P wave receiver function stacks to constrain P wave azimuthal anisotropy in the core-mantle boundary, with a particular focus on the regions of possible slab graveyard, ULVZs and the base of LLVPs. These renewed descriptions of P wave anisotropy models will be used to explore outstanding questions including the rheology or the deformation mechanism, the mantle flow patterns near the core-mantle boundary and the nature of LLVPs and ULVZs.A series of outstanding questions can be much better addressed with our new seismic observations:What's the rheology and deformation mechanism operating in the D'' layer? How did the slab graveyard, LLVPs and ULVZs deform and their anisotropy properties? Are LLVPs and ULVZs compositional distinctly from the rest of the D'' layer?Is the deformation accommodated by bridgmanite, post-perovskite or secondary minerals such as ferropericlase and calcium-perovskite? Is the dislocation creep, responsible for upper mantle seismic anisotropy, operating in the D'' layer?These unprecedentedly rich observations will provide renewed constraints on fundamental processes relevant to the Earth's interior and evolution.

虽然地球表面标志着大气和固体地球之间的边界，但核-地幔边界(CMB)将固体地幔与液体核分开，调节热量的损失，并驱动地球的发电机和磁场。限制CMB地区的地震各向异性是具有挑战性的。前人关于S波各向异性的研究结果在地理采样、方位覆盖或(或)对上地幔地震各向异性的适当校正等方面受到一定的限制，这是不小的。以前的研究，无论是单独进行，还是在区域或全球范围内联合进行，都没有对D‘’层中的P波方位各向异性做出任何估计。超低速区(ULVZ)、大低速区(LLVP)或板岩墓地的P波各向异性特性尚不清楚，我们将利用径向P波接收函数叠加法中新观测到的岩心绕射PcSdiff波来约束核幔边界的P波方位各向异性，重点关注可能的板岩墓地、ULVZ和LLVEP底部区域。这些新的P波各向异性模型的描述将被用来探索悬而未决的问题，包括流变学或变形机制，核幔边界附近的地幔流动模式，以及LLVP和ULVZ的性质。我们的新地震观测可以更好地解决一系列悬而未决的问题：D‘’层的流变学和变形机制是什么？板岩墓地、LLVP和ULVZ是如何变形及其各向异性的？LLVP和ULVZ的成分是否与D‘’层的其余部分截然不同？变形是由桥镁矿、后钙钛矿还是次生矿物如钙镁石铁和钙钙钛矿所适应的？造成上地幔地震各向异性的位错蠕动是在D‘’层进行的吗？这些空前丰富的观测结果将为与地球内部和演化相关的基本过程提供新的约束。