Self‐Consistent Models of Earth's Mantle and Core From Long‐Period Seismic and Tidal Constraints

Abstract Here we illustrate the use of parameterized models to address fundamental questions about Earth's mantle and core structure. For this, we invert a large set of normal‐mode center frequencies and quality (attenuation) factors, along with astronomic‐geodetic data, for the radial anelastic seismic structure of the Earth. We consider two distinct parameterizations that rely on physically and polynomially parameterized models. In the first 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 years), whereas seismic properties for a homogeneous and adiabatic core are computed using equations‐of‐state. The polynomially parameterized 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 quantify uncertainty estimates on the derived structure—a feature absent from radial seismic reference models—we employ a stochastic sampling‐based approach in solving the inverse problem. To further constrain mantle and outer‐core seismic wave velocity structure, we also inverted globally‐averaged P‐ and S‐wave and multiple core‐mantle boundary underside‐reflected S‐wave travel times, respectively. The results indicate considerable deviations from PREM, including a denser outer core and less dense inner core, and thus a diminished density contrast across the inner‐core boundary. Also, outer‐core stratification, associated with the layer, appears not to be required to match data. Finally, and of general interest to the wider community, uncertainty measures on all inverted properties are provided with the models presented here.