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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. Prior to this project, the AfricaArray seismic network included about 20 seismic stations in eastern and southern Africa equipped with a variety of data loggers and sensors, many of them very old. The data loggers and many of the sensors at those stations have been replaced with new, state-of-the-art equipment, including RefTek 24-bit data loggers and Guralp and Nanometrics broadband sensors. In addition, equipment has been purchased and installed in 30 new stations, bringing the size of the network to 50 stations in 19 African countries spanning western, southern, and eastern Africa, as well as Madagascar. Most of the stations are stand alone stations with data downloads done manually every few months, but a few of them are connected to the internet and provide data in near real time. The stations are powered with solar panels and batteries. The stations are operated by local host institutions, which include geological surveys, universities and meteorological organizations. Funding from this grant has also been used to purchase spare equipment to keep the network running well into the future. A map of the stations can be found on the AfricaArray web site (www.AfricaArray.org). The data from the network are archived at the Incorporated Research Institutions for Seismology (IRIS) data management center under the AF netwrok code. The data from twelve of the stations open as soon as the data reach the archive. Data from the remaining stations are openly released three years after they are collected. The data are being used by AfricaArray partners in a variety of research projects involving the training of undergraduate and graduate students. The projects include seismicity studies in areas with active seisimc hazards, imaging of shallow earth structure in regions with potential for hosting mineral and petroleum deposits, and deep earth structure. There are many students in Africa and the U.S. who have used data from the AfricaArray network of M.S. and Ph.D. thesis research, and more than 50 papers in peer reviewed journals have been published using data from the network.
