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

下地幔几个突出地震异常的高分辨率绘图

• 批准号: 0911319
• 负责人: Lianxing Wen
• 金额: $ 27.61万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2012-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911319&HistoricalAwards=false
• 关键词: resolution; mapping; several; prominent; seismic

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.

地震证据表明，存在两个突出的地震低速异常的地球？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异、演化和动力学直接相关。的斗篷。因此，解决这两个异常的详细结构和速度特征是重要的，以进一步了解我们的地球？导致地球地质事件和构造活动的内部过程？该提案旨在基于广泛的波形建模和旅行时分析来解决与太平洋异常相关的未决问题，并研究地幔几个特定区域的详细三维各向异性、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。与太平洋异常有关的重要问题包括：核幔边界异常的确切地理范围，其他剖面异常的结构和速度特征，太平洋异常向周围地幔各方向的详细过渡结构，以及异常与周围地幔的相互作用。以及异常底部小尺度异常的构造特征、长度尺度和速度衰减的横向变化。提出的方法包括开发混合各向异性方法;收集和识别高质量的异常地震数据;对地震数据进行波形和旅行时建模，其科学目标是绘制下地幔三个突出速度异常的详细结构特征和速度结构。除了培养一名研究生和提供混合方法的社区计算机源代码外，该提案还将进一步加深我们对地球热演化、地幔热化学对流、地幔热化学柱、地幔地震非均匀性与地球早期分异的关系、热点运动特征、独特的地球化学标志，包括DUPAL异常和南太平洋同位素和热异常。