Collaborative Research: Africa Array--Imaging the African Superplume

非洲超级羽流是非洲南部下地幔中一大片地震波速度较低的区域，长期以来一直被认为是地幔最显著的特征之一。非洲超级羽流的上方是非洲超级井，这表明下地幔动力学与形成非洲板块的地质过程之间存在地球动力学联系。非洲超级羽流的起源和性质是有争议的。对非洲南部低波速区域的最初解释将其归因于长期存在的热地幔上升流。此后的许多地震研究表明，超级羽流中存在化学不均匀性。超级羽流异常的哪些部分是热的，哪些是化学的（或两者都有）仍然不确定，它的起源也是如此。在这个项目中，非洲超级羽流的结构、组成和起源将利用非洲阵列前三年的宽带地震数据以及现有数据进行调查，并集中进行四种分析；1)利用体波传播时间对上地幔和下地幔进行层析成像；2)模拟Superplume样本的远震体波相位波形；3)联合反演地壳和上地幔结构的接收函数和面波频散测量；4)叠加和迁移接收函数以成像410和660 km间断面上的地形。africarray项目是一个新的为期10年的泛非地球物理学培训和研究项目，重点放在地震学上，由威特沃特斯兰德大学、地球科学委员会（南非地质调查局）和宾夕法尼亚州立大学建立。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。“非洲计划”将大大加强美国地球物理学界与非洲各地地球科学家之间的科学联系。一旦成立，africaarray将通过夏季实习和夏季地球物理实地课程（都在非洲）向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.