Upper mantle anisotropy beneath the African IRIS and Geoscope stations

Upper mantle anisotropy beneath the African IRIS and Geoscope stations is i nvestigated through the measurements of splitting of teleseismic shear wave s such as SKS, SKKS and PKS phases. Seismic anisotropy data are interesting on their own as a measure of upper mantle active or frozen deformation ben eath a given station, but each station is of potential interest since it ca n be used to retrieve source-side seismic anisotropy at remote sites if one is able to perform station-side anisotropy correction. We performed system atic investigations of teleseismic shear wave splitting at 15 stations from the IRIS and Geoscope global seismic networks, which are located on both t he oceanic and the continental parts of the African plate. Anisotropy is ge nerally well observed at continental stations. The patterns we present gene rally show much more complexity than the results previously published from smaller data sets. Despite this complexity, the splitting parameters genera lly appear in several places to contain a signature of the regional geodyna mic setting (rift structures, Archaean craton, Pan-African belt), although a deeper source of anisotropy (asthenospheric) may be present. At the ocean ic stations, anisotropy measurements are much more difficult to perform bec ause the signal is generally of poor quality. MSEY, in the Seychelles (Indi an ocean), is the exception and displays a clear correlation of the azimuth of the fast split shear wave with the trend of the absolute plate motion, as defined by hotspot tracks.