Nov. 13, 2019,
noon - 1 p.m.
As a major interface in the solid-Earth, the 660-km discontinuity plays a critical role in our understanding of mantle geodynamics. Various seismic methods have been exploited to detect its properties, including sharpness, impedance contrast and topography. In this talk, I will present the observations of back-scattering seismic waves P'●660●P' and explain the constraints they provide on small-scale topography of the 660-km discontinuity. This small-scale topography must be caused by chemical heterogeneities, because any thermal anomalies in the deep earth would be smoothed out at a geological scale. I will discuss the possible interpretations of these chemical heterogeneities and their implications in the mantle material recycling.