Collaborative Research: A dynamic mechanism for generating directional variation of seismic velocities in the Earth's inner core

The inner core is a ball of solid iron that sits at the Earth’s center. It is 2000 km across, as hot as the surface of the sun, and experiences 3 million times the pressure of the atmosphere. The inner core helps to control the planet’s magnetic field and contributes to Earth being habitable, unlike Mars. Although humans may never visit the inner core, researchers can use seismic waves from earthquakes to determine inner core properties. They can also build computer models of its flow behavior to understand how it evolves. This project will use both approaches to better understand the dynamics and complexity of the inner core. Students will be trained in computational geodynamics, seismology, and high-performance computing. In addition to developing better understanding of Earth's inner core, the research will offer new insight into how planetary interiors behave, with implications for understanding other rocky planets in our solar system and beyond. Seismic studies show that the inner core is not uniform but instead shows directional variations in elastic wave speeds (anisotropy) and other large-scale hemispherical differences. These features reveal a dynamic and complex interior. However, the processes responsible for forming and maintaining these differences are poorly understood. This project builds a geodynamical model that couples thermal, mechanical, and seismic constraints. The model will provide a self-consistent framework for understanding the generation of the observed inner core anisotropy. The hypothesis is that anisotropic thermal conductivity of iron crystals causes the heat transport in the inner core to depend on crystal orientation. Thus, the presence of preferred crystal orientation generates spatial variations in heat flux that produce temperature anomalies within the bulk inner core. Under these conditions, the associated thermal buoyancy drives flow producing stresses that align crystals and reinforce existing texture. To test this mechanism, the project will develop a time-dependent model incorporating anisotropic heat transport, viscous deformation, and evolving texture. This model will explore the effects of initial crystal alignment, stratification and heterogeneity length-scale to determine whether these factors can explain the present-day observed structure of the inner core. The research will integrate mineral physics constraints and link microscale deformation mechanisms to macroscale seismic signatures. This will enable direct comparison between model predictions and seismic anisotropy measurements. The project aims to bridge the gap between the seismic observations, geodynamic modeling, and mineral deformation mechanisms, ultimately leading to a more complete understanding of Earth's inner core. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2534052 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Bruce Buffett | Institution: University of California-Berkeley, BERKELEY, CA | Award Amount: $269,085 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2534052 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2534052.html