A Combined Geodynamic-Tomography Investigation into Thermochemical Piles in the Lower Mantle beneath Africa and the Pacific

Seismic tomography reveals large, low-velocity anomalies in the lower mantle beneath Africa and the Pacific. Heterogeneous mantle models typically place the anomalies into the context of thermochemical piles, characterized by a different, denser composition than the surrounding region. We investigate these structures using spherical thermochemical and isochemical convection calculations with imposed Earth-like boundary conditions. Due to the heterogeneous resolution of tomographic models, we must carefully compare our numerical models to the tomographic models. We choose to filter the numerical images by convolving them with the resolution matrix of the tomographic model S20RTS. This filter applies the inversion artifacts of S20RTS to the numerical models, allowing us to investigate the "blurring and smearing" that compromise the quality of the seismic images, and their effect on model interpretation. We develop statistical correlation methods to compare filtered geodynamic model predictions to observed tomography. We aim to investigate the necessity of a thermochemical component to produce the anomalies in the lower mantle observed by tomography. The procedure of tomographically filtering geodynamic model data may lead to a more-detailed, reliable understanding of the parameters required in geodynamic models to produce the anomalous structures observed beneath Africa and the Pacific.