Shear Wave Splitting Across Eastern, Western and Southern Africa

Andrew Nyblade, Pennsylvania State University, Department of Geosciences, University Park, United States, Cristo Ramirez, Penn St Univ, University Park, PA, United States, Brian C Bagley, University of Minnesota Twin Cities, Minneapolis, MN, United States, Gabriel Daudi Mulibo, University of Dar es Salaam, Dar es Salaam, Tanzania, Fred Tugume, Geological Survey Department, Entebbe, Uganda, Michael Edward Wysession, Washington University in St Louis, Saint Louis, United States and Douglas Wiens, Washington University in St. Louis, Department of Earth and Planetary Sciences, St. Louis, United States
Abstract:
The expansion of the AfricaArray network across eastern, western and southern Africa, in conjunction with seismic data from many PASSCAL deployments over the past 20 years, is helping to fill in major gaps in the global coverage of shear wave splitting measurements. New results from stations in Ghana, Nigeria, Mozambique, Botswana, Angola, Namibia and South Africa are presented in this study that when combined with previously published measurements help to map the pattern of seismic anisotropy over much of the African continent. A general pattern of fast polarization directions, characterized by NE orientations, is found, and superimposed on this subcontinental-scale pattern is local and regional variability, most notably around the Archean Tanzania craton in eastern Africa. The subcontinental-scale pattern, as well as local and regional variations in this pattern, are interpreted in terms of large-scale mantle flow from the African Superplume, fossil anisotropy in the lithosphere, and shape anisotropy in magmatic regions of the East African rift system.
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