Self-consistent models of Earth's mantle and core from long-period seismic and tidal constraints

Here we illustrate the use of self-consistent models to address fundamental questions about Earth's mantle and core structure. For this purpose, we invert a large set of recent normal-mode centre frequencies and quality (attenuation) factors, along with astronomic-geodetic data (mass, moment of inertia and tidal response), for the radial anelastic seismic structure of the Earth. We consider two distinct parameterisations that rely on 1) self-consistent and 2) physically-parameterised models. In the self-consistent approach, mantle models are constructed using petrologic phase equilibria in combination with a laboratory-based viscoelastic model connecting dissipation from seismic to tidal periods (~100~s--20~yr), whereas seismic properties for a homogeneous and adiabatic core are computed using equations-of-state. The physically-parameterised models follow the preliminary reference Earth model (PREM) and rely on a polynomial representation of density, P- and S-wave velocity, attenuation, and anisotropy. To study the impact of the inferred mantle seismic velocity structure, we compute P- and S-wave travel times and compared these to the observations of globally-averaged body wave travel times from the reprocessed ISC catalog. To further refine the seismic P-wave velocity structure of the outermost outer core, we also consider multiple core-mantle-boundary underside-reflected body wave travel times. The results indicate deviations from PREM, including a denser outer core, which possibly reduces the requirement for light elements, while diminishing the density contrast across the inner-core boundary. Finally, and of general interest to the wider community, uncertainty measures on all inverted properties are provided with the models presented here.