Collaborative Research: Africa Array - Imaging the Africa Super Plume

合作研究：非洲阵列-成像非洲超级地幔柱非洲超级地幔柱是南部非洲下地幔中的一个大的低地震波速度区域，长期以来一直被认为是地幔最突出的特征之一。在非洲超级地幔柱之上是非洲超级深井，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。非洲超级羽流的起源和性质存在争议。最初对非洲南部低波速区的解释是，它是一个长期存在的热地幔上涌。从那时起，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还是化学的（或两者兼而有之）仍然不确定，其起源也不确定。在该项目中，将利用非洲阵列头三年的宽带地震数据以及现有数据，对非洲超级地幔柱的结构、组成和起源进行调查，并侧重于四类分析; 1）使用体波传播时间的上地幔和下地幔的层析成像，2）模拟对超级地幔柱进行采样的地球物理体波相位的波形，3）联合反演接收器函数和面波频散测量，以了解地壳和上地幔结构; 4）叠加和迁移接收器函数，以成像410和660公里不连续面上的地形。由威特沃特斯兰德大学、地球科学理事会（南非地质调查局）和宾夕法尼亚州立大学设立。AfricaArray将为美国地球物理学界提供多年来有关地球结构和过程的重要地震数据。非洲阵列将大大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，AfricaArray将通过暑期实习和暑期物理学实地课程（均在非洲）为美国少数民族群体以及其他学生提供促进物理学的机会。

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.