GrowYourIC: A Step Toward a Coherent Model of the Earth's Inner Core Seismic Structure

A complex inner core structure has been well established from seismic studies, showing radial and lateral heterogeneities at various length scales. Yet no geodynamic model is able to explain all the features observed. One of the main limits for this is the lack of tools to compare seismic observations and numerical models successfully. We use here a new Python tool called GrowYourIC to compare models of inner core structure. We calculate properties of geodynamic models of the inner core along seismic raypaths, for random or user-specified data sets. We test kinematic models which simulate fast lateral translation, superrotation, and differential growth. We explore first the influence on a real inner core data set, which has a sparse coverage of the inner core boundary. Such a data set is however able to successfully constrain the hemispherical boundaries due to a good sampling of latitudes. Combining translation and rotation could explain some of the features of the boundaries separating the inner core hemispheres. The depth shift of the boundaries, observed by some authors, seems unlikely to be modeled by a fast translation but could be produced by slow translation associated with superrotation. Plain Language Summary The Earth's inner core is the solid part of the Earth's core located at the very center of the Earth. It is slowly crystallizing from the liquid outer core, powering the geodynamo and generating the magnetic field. The inner core's structure, detected via observations of seismic waves, is complex and still not elucidated. No model has yet been successful at explaining its different features, and questions as simple as when did the inner core started crystallizing are still unanswered. In this work, we propose a new framework to study seismic properties of the inner core, combining models of how materials flow and seismic data set. We developed an open-access and easy-to-use software to compare both predictions and real data. This toolbox will help us understand what is happening at the very center of our planet, and rule out proposed models. By understanding the inner core dynamics, we hope to better comprehend the thermal and compositional history of the deepest parts of our planet.