Collaborative Research: Africa Array--Imaging the African Superplume

合作研究：非洲阵列-成像非洲超羽流非洲超羽流是非洲南部下地幔的一大片低地震波速度区域，长期以来一直被认为是地幔最显著的特征之一。在非洲超级羽流上方是非洲超级井，这表明下地幔动力学和塑造非洲板块的地质过程之间存在地球动力学联系。非洲超强羽流的起源和性质存在争议。对南部非洲下方低波速区域的最初解释将其归因于长期的、高温的地幔上升。从那时起，许多地震研究表明，超羽流内部存在化学不均匀。超羽流异常的哪一部分是热的还是化学的(或两者兼而有之)仍不确定，其来源也是如此。在这个项目中，将利用非洲阵列最初3年的宽带地震数据，结合现有数据，调查非洲超烟羽的结构、组成和来源，并集中进行四种类型的分析；1)利用体波走时对上地幔和下地幔进行层析成像，2)对远震体波相进行采样，3)联合反演接收函数和地壳和最上地幔结构的面波频散测量，以及4)叠加和偏移接收函数以成像410和660公里不连续面上的地形。非洲阵列将为美国地球物理界提供多年来有关地球结构和过程的重要地震数据。非洲阵列将极大地加强美国地球物理学界和整个非洲地球科学家之间的科学联系。一旦成立，非洲阵列将通过暑期实习和暑期地球物理野外课程(均在非洲)为美国少数群体以及其他学生提供推广地球物理学的机会。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。

Collaborative Research:AfricaArray - Imaging the African SuperplumeThe African Superplume is a large region of low seismic wave speeds in the lower mantle under southern Africa that has long been recognized as one of the most prominent features of the mantle. Above the African Superplume lies the African Superswell, suggesting a geodynamic link between lower mantle dynamics and geologic processes shaping the African plate. The origin and nature of the African Superplume is controversial. The initial interpretation of the low wave speed region under southern Africa attributed it to a long-lived, hot mantle upwelling. A number of seismic studies since then have suggested the presence of chemical heterogeneity within the superplume.What parts of the superplume anomaly are thermal vs. chemical (or both) remains uncertain, as does its origin. In this project, the structure, composition and origin of the African Superplume will be investigated using the first 3 years of broadband seismic data from AfricaArray, together with existing data, and concentrating on four types of analyses; 1) tomographic imaging of the upper and lower mantle using body wave travel times, 2) modeling waveforms of teleseismic body wave phases that sample the Superplume, 3) jointly inverting receiver functions and surface wave dispersion measurements for crust and uppermost mantle structure, and 4) stacking and migrating receiver functions to image topography on the 410 and 660 km discontinuities.AfricaArrayis a new 10-year-long Pan-African training and research initiative in geophysics, with an emphasis on seismology, set up by the University of the Witwatersrand, the Council for Geoscience (South African geological survey), and Penn State. AfricaArraywill provide the U.S. geophysics community with important seismic data on earth structure and processes for many years. AfricaArraywill greatly strengthen scientific ties between the U.S. geophysics community and earth scientists throughout Africa. Once established, AfricaArraywill provide opportunities for promoting geophysics to U.S. minority groups, as well as other students, through summer internships and a summer geophysics field course (both in Africa).This award is co-funded by NSF's Office of International Science and Engineering.