[S-IT16] Planetary cores: Structure, formation, and evolution

[SIT16-10] The thermal and compositional patterns of Earth’s inner core inferred from novel seismic measurement techniques

★Invited Papers

*Lauren Waszek¹, Hrvoje Tkalcic², Thuany Costa de Lima², Anatoly Belonoshko³, Jack Muir⁴, Maurizio Mattesini^5,6, Louis Moresi² (1.James Cook University, 2.Australian National University, 3.Royal Institute of Technology, 4.Space Fleet Technologies, 5.Complutense University of Madrid, 6.Facultad de Ciencias Físicas)

Keywords:Inner core, Seismology, Anisotropy, Attenuation, Dynamics

Advancements in our knowledge of Earth’s inner core properties are hampered by limited seismic resolution, which results from uneven sampling in global body wave coverage. Recent studies benefit from an ongoing expansion in seismic stations, however developments in observational techniques are emerging as a major factor for enhancing resolution. These measurements form the inputs for models of inner core dynamics and composition, and hence better understanding of Earth’s inner core evolution.

Here, we discuss emerging novel seismic observational methodologies: the global coda-correlation wavefield, and transdimensional statistic tomography. We present two new sets of measurements, each compiled based on one of these techniques, to showcase their significant potential for improving inner core resolution. A Bayesian tomographical inversion produces new isotropic velocity and attenuation models for the upper inner core, while coda-correlation data analysis provides insight into the unique anisotropic structure of the innermost inner core.

Our seismic measurements are evaluated within the context of mineral physics calculations, heat flow analysis, and dynamical modelling. Results for the upper inner core support a more complex style of thermal flux than the previously-proposed hemispheres; internally driven inner core convection is a plausible candidate model to create this pattern. For the innermost inner core, the observations confirm a distinct anisotropy, oriented differently to that in the bulk of the inner core. This transition in anisotropy suggests a dynamic event during the early stages of inner core formation, imprinted during the texturing and solidification processes of its growth.