Upper mantle discontinuity topography from thermal and chemical heterogeneity.

Supporting Online Material for Upper Mantle Discontinuity Topography from Thermal and Chemical Heterogeneity

Hydrous upwelling across the mantle transition zone beneath the Afar Triple Junction

The mechanisms that drive the upwelling of chemical heterogeneity from the lower to upper mantle (e.g., thermal versus compositional buoyancy) are key to our understanding of whole mantle convective processes. We address these issues through a receiver function study on new seismic data from recent deployments located on the Afar Triple Junction, a location associated with deep mantle upwelling...

An analysis of SS precursors using spectral-element method seismograms

The traveltimes of underside shear wave reflections (i.e. SS precursors) are widely used data for mapping the topography of mantle discontinuities in the upper mantle. Here, we examine the accuracy of ray theory in estimating the contribution of shear velocity heterogeneity in the mantle to SS–S400S, SS–S670S and S400S–S670S traveltimes. We analyse stacks of spectral-element method waveforms co...

Three-Dimensional Simulations of Mantle Convection with a Thermo-Chemical Basal Boundary Layer: D”?

Numerical simulations in both twoand three-dimensions are performed to investigate the hypothesis that D” is a thermo-chemical boundary layer. A layer of dense, compositionally-distinct material above the CMB reduces the characteristic horizontal lengthscales and interior mantle temperature. In three-dimensions, the layer forms a spoke pattern, with entrainment in upwelling cylinders, even for ...

Splitting of the 520-kilometer seismic discontinuity and chemical heterogeneity in the mantle.

Seismic studies indicate that beneath some regions the 520-kilometer seismic discontinuity in Earth's mantle splits into two separate discontinuities (at approximately 500 kilometers and approximately 560 kilometers). The discontinuity near 500 kilometers is most likely caused by the (Mg,Fe)2SiO4 beta-to-gamma phase transformation. We show that the formation of CaSiO3 perovskite from garnet can...