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.

地球表面标志着大气层和固体地球之间的边界，而地核-地幔边界 (CMB) 将固体地幔与液体地核分开，调节热量损失并驱动地球的发电机和磁场。 CMB 地区充满挑战。先前关于S波各向异性的结果在地理采样、方位角覆盖或/和上地幔地震各向异性的适当校正方面受到一些限制，这并非微不足道。以前的研究，无论是单独的还是组合的、区域性的还是全球性的，都没有对 D'' 层中 P 波方位各向异性进行任何估计。我们不知道超低速区 (ULVZ)、大型低速区 (LLVP) 或板墓地的 P 波各向异性特性。我们将使用径向 P 波接收器函数堆栈中核心衍射 PcSdiff 波的新颖观测来约束核幔边界中的 P 波方位各向异性，特别关注可能的板片墓地、ULVZ 和 LLVP 底部的区域。这些对 P 波各向异性模型的重新描述将用于探索悬而未决的问题，包括流变或变形机制、核幔边界附近的地幔流动模式以及 LLVP 和 ULVZ 的性质。一系列悬而未决的问题可以得到更好的解决我们新的地震观测结果解决了这个问题：D''层的流变和变形机制是什么？板墓场、LLVP 和 ULVZ 是如何变形的以及它们的各向异性特性？ LLVP 和 ULVZ 的成分是否与 D'' 层的其余部分明显不同？变形是否由桥锰矿、后钙钛矿或次生矿物（例如铁方镁石和钙钙钛矿）调节？导致上地幔地震各向异性的位错蠕变是否在 D'' 层中起作用？这些前所未有的丰富观测将为与地球内部和演化相关的基本过程提供新的约束。