High-resolution mapping of several prominent seismic anomalies in the lower mantle

地震证据表明地球上存在两个显著的地震低速异常。即太平洋异常和非洲异常。现在人们认识到，这两个突出的异常可能与地球的早期分化、演化和动力学直接相关。地幔。因此，解决这两个异常的详细结构和速度特征对我们进一步了解地球是很重要的。什么是导致地球地质事件和构造活动的内部过程？年代的表面。本课题拟在广泛的波形建模和走时分析的基础上，解决太平洋异常相关的突出问题，详细研究地幔若干特定区域的三维各向异性、结构特征和速度结构，包括a)非洲异常边缘附近的各向异性结构；b)科科斯板块下非洲异常东南缘和高速异常西缘的构造特征和速度结构。太平洋异常需要解决的重要问题包括：异常在核幔边界的确切地理范围；其他剖面的构造和速度特征；从太平洋异常到周围地幔各方向的详细过渡构造；以及异常基底小尺度异常的构造特征、长度尺度和速度消减的横向变化。提出的方法包括开发一种混合各向异性方法；高质量异常地震资料的收集与识别并对地震数据进行波形和走时建模，以绘制下地幔三个显著速度异常的详细结构特征和速度结构。除了培养研究生和提供混合方法的社区计算机源代码外，该建议还将进一步加深我们对地球热演化，地幔热化学对流，地幔热化学羽流，地幔地震非均质性与地球早期分异的关系，热点运动特征，独特的地球化学特征，包括DUPAL异常和南太平洋同位素和热异常。

Seismic evidence indicates the existence of two prominent seismically low-velocity anomalies in the Earth?s lower mantle, namely the Pacific Anomaly and the African Anomaly. It is now recognized that these two prominent anomalies may directly be related to the early differentiation, evolution and dynamics of the Earth?s mantle. Thus, resolving the detailed structural and velocity features of these two anomalies is important to further our understanding of the Earth?s internal processes that lead to the geological events and tectonic activities at the Earth?s surface.This proposal intends to resolve the outstanding issues related to the Pacific Anomaly based on extensive waveform modeling and travel time analysis, and to study detailed 3D anisotropy, structural feature and velocity structure in several particular regions of the mantle, including a) anisotropic structure near the edge of the African Anomaly, and b) structural feature and velocity structure of the southeastern edge of the African Anomaly and the western edge of the high-velocity anomaly beneath the Cocos plate. The important outstanding issues related to the Pacific Anomaly to be addressed include: the exact geographic extent of the Anomaly at the core-mantle boundary; the structural and velocity features of the Anomaly in other cross sections; the detailed transitional structures from the Pacific Anomaly to the surrounding mantle in various directions; and the lateral variations of structural feature, length-scale and velocity reductions of small-scale anomalies at the base of the Anomaly. The proposed approaches include development of a hybrid anisotropic method; collection and identification of high-quality anomalous seismic data; and waveform and travel time modeling of the seismic data with a scientific goal of mapping detailed structural features and velocity structures of the three prominent velocity anomalies in the lower mantle. Besides training a graduate student and providing the community computer source code for a hybrid method, the proposal would further our understanding of the thermal evolution of the Earth, thermal-chemical convection in the mantle, thermal-chemical mantle plume, and relationship of mantle seismic heterogeneities to early differentiations of the Earth, the characteristics of the hotspot motions, and the unique geochemical signatures including the DUPAL anomaly and the South Pacific Isotopic and Thermal Anomaly.