AfricaArray is a 3-year-old multi-faceted initiative to promote coupled educational and research programs for 1) building science capacity in the U.S. and Africa 2) addressing fundamental science questions in Africa of academic, economic and societal importance, and 3) enhancing diversity in the geosciences, both in the U.S. and Africa. At the core of AfricaArray is a network of 26 permanent seismic stations spanning 11 countries in eastern and southern Africa that has been built cooperatively by seismic network operators across Africa, with assistance from U.S. and European scientists, to form a shared research facility that serves African and U.S. scientists alike.
In this project, the AfricaArray seismic network will be upgraded and expanded to provide the definitive seismic data set for imaging the largest geophysical anomaly in Earth's mantle, the African superplume. Data from the upgraded and expanded seismic network will allow scientists to address several first-order, inter-related questions focused on the structure and dynamics of the African superplume. 1) What is the nature and origin of the African superplume? 2) What is the geodynamic relationship between the African superplume and mantle convection? 3) What are the dynamics of upper mantle convection under the east African rift system and plateau and how does it relate to the African superplume structure under southern Africa? 4) What is the structure of African cratonic lithosphere and how does it influence mantle dynamics beneath the African plate?
Determining the chemical and dynamic causes of the African superplume and defining its relation to shallower mantle structure and surface processes (uplift, rifting, volcanism) is arguably the most important issue in understanding the dynamics of the deep mantle. Seismic images will play a key role in gaining this understanding.
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Funding was used to upgrade and expand the AfricaArray permanent seismic network, which constitutes the fundamental infrastructure behind a multi-faceted initiative to promote educational and research programs for 1) addressing fundamental science questions of academic, economic and societal importance, 2) building science capacity in Africa and the U.S., and 3) enhancing diversity in the geosciences, both in Africa and the U.S. During the course of this grant, UT Austin acquired ten Reftek digitizer/recorders and six Nanometrics Trillium Compact seismometers, along with sundry cables, that allowed AfricaArray to install seismic stations in new countries, expanding its geographical coverage, and to replace borrowed and aging equipment in other locations. The seismic network’s expansion aided AA’s academic, diversity, and research programs, particularly the effort to image the Africa superplume. The African superplume is both one of the most prominant features of the Earth’s mantle. Covering much of the southern African subcontinent, it is characterized by seismic wave velocities that are lower than other structures in the Earth’s lower mantle. The superplume lies beneath an area with an anomalously high topography, suggesting a geodynamic relationship between the superplume and the formation of plateaus and rift valleys in eastern and southern Africa. Research emanating from AfricaArray include tomographic imaging of the upper and lower mantle using body wave travel times; modeling waveforms of teleseismic body wave phases that sample the superplume; jointly inverting receiver functions and surface wave dispersion measurements for crust and uppermost mantle structure; and stacking and migrating receiver functions to image topography on the 410 and 660 km discontinuities. Data recorded by the new seismic stations also provided data to students involved in AfricaArray’s innovative "sandwich" program. To increase AfricaArray’s training capacity at the M.Sc. and Ph.D. levels, a program was created in which students spend up to six months each year studying and doing research with a professor at one of the AfricaArray-affiliated Universities in the U.S. or Europe.
