Lowermost mantle flow at the eastern edge of the African Large Low Shear Velocity Province

摘要: Abstract Observations of seismic anisotropy in the lowermost mantle are plentiful, but their interpretation terms flow remains challenging. Here we interrogate anisotropic structure beneath Afar region, just outside edge African Large Low Shear Velocity Province, using a combination shear wave splitting techniques applied to phases propagating at five distinct raypath orientations. We then model resulting data set by testing various candidate mechanisms for anisotropy. The observations best fit that invokes lattice preferred orientation (LPO) post-perovskite, with [100] crystallographic axis oriented either nearly vertically or highly obliquely horizontal plane. Plausible corresponding scenarios involve significant vertical component, which suggests Province may deflect ambient upwards be associated sheet-like upwelling.