The origin of widespread volcanism far from plate boundaries and mantle plumes remains a fundamental unsolved question. An example of this puzzle is the Anatolian region, where abundant intraplate volcanism has occurred since 10 Ma, but a nearby underlying plume structure in the deep mantle is lacking. We employed a combination of seismic and geochemical data to link intraplate volcanism in Anatolia to a trail of magmatic centers leading back to East Africa and its mantle plume, consistent with northward asthenospheric transport of over ~2500 km distance. Joint modeling of seismic imaging and petrological data indicates that the east Anatolian mantle potential temperature is higher than the ambient mantle (~1420C). Based on multiple seismic tomography models, the Anatolian upper mantle is likely connected to East Africa by an asthenospheric channel with low seismic velocities. Along the channel, isotopic signatures among volcanoes are consistent with a common mantle source, and petrological data demonstrate similar elevated mantle temperatures, consistent with little cooling in the channel during the long-distance transport. Horizontal asthenospheric pressure gradients originating from mantle plume upwelling beneath East Africa provide a mechanism for high lateral transport rates that match the relatively constant mantle potential temperatures along the channel. Rapid long-distance asthenospheric flow helps explain the widespread occurrence of global intraplate magmatism in regions far from deeply-rooted mantle plumes throughout Earth history.

This study presents an improved approach to common-conversion point stacking of converted body waves that incorporates scattering kernels, accurate and efficient measurement of stack uncertainties, and an alternative method for estimating free surface seismic velocities. To better separate waveforms into the P and SV components to calculate receiver functions, we developed an alternative method to measure near surface compressional and shear wave velocities from particle motions. To more accurately reflect converted phase scattering kernels in the common-conversion point stack, we defined new weighting functions to project receiver function amplitudes only to locations where sensitivities to horizontal discontinuities are high. To better quantify stack uncertainties, we derived an expression for the standard deviation of the stack amplitude that is more efficient than bootstrapping and can be used for any problem requiring the standard deviation of a weighted average. We tested these improved methods on Sp phase data from the Anatolian region, using multiple bandpass filters to image velocity gradients of varying depth extents. Common conversion point stacks of 23,787 Sp receiver functions demonstrate that the new weighting functions produce clearer and more continuous mantle phases, compared to previous approaches. The stacks reveal a positive velocity gradient at 80-150 km depth that is consistent with the base of an asthenospheric low velocity layer. This feature is particularly strong in stacks of longer period data, indicating it represents a gradual velocity gradient. At shorter periods, a lithosphere-asthenosphere boundary phase is observed at 60-90 km depth, marking the top of the low velocity layer.

Seismic anisotropy provides insight into past episodes of lithospheric deformation and the orientations of strain in the underlying asthenosphere. The Greenland mantle has played host to a rich history of tectonic processes, including multiple orogenies and plume-lithosphere interactions. This study presents new measurements of SKS splitting that reveal strong variations in fast polarization direction with back-azimuth that are consistent across Greenland, including at stations where splitting measurements have not previously been reported. We compared observed fast polarization directions to the predictions of two-layer models with olivine-orthopyroxene anisotropy. The family of models which provides acceptable misfits at 95% confidence indicates an upper layer olivine a-axis azimuth of 226 +/- 2.9{degree sign} and a lower layer olivine a-axis azimuth of 124 +/- 2.7{degree sign} and non-zero axis dips are required. These models are consistent with asthenospheric anisotropy aligned approximately parallel to the direction of plate motion and lithospheric anisotropy due to Proterozoic and Archean orogenic fabrics.