Model of Topography and Impedance Contrasts Across the 660-Km Discontinuity

The globally observed seismic discontinuity at 660 km depth due to the post-spinel phase transition plays a key role in the style of material circulation within the mantle. While the topography of the 660 has been extensively investigated based on arrival times of long-period reflected, converted and coda waves, the amplitudes of these seismic arrivals, which are sensitive to density variations at the boundary, have not been sufficiently explored to date. In this study, we take advantage of a global dataset of SS precursors and simultaneously constrain the global variations of discontinuity depth, shear velocity and density contrasts across the 660. Please read the README file for a detailed description of the model.