Abstract:

Stacks of short-period precursors to the seismic core phase PKP reveal details of the precursor amplitudes that can be used to constrain the depth extent of mantle scattering. The simplest model consistent with the observations contains small (8 km scale length), weak (1% rms velocity perturbation) random heterogeneities uniformly distributed throughout the entire mantle. The data do not support an increased concentration of scatters within the D'' layer at the base of the mantle and limit the amplitude of any short-wavelength CMB topography.