Slow Earth's Inner Core Motion

Session: Advances in Seismic Imaging of Earth’s Mantle and Core and Implications for Convective Processes [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The Earth's solid inner core, which is surrounded by the liquid outer core, is not attached to the overlying mantle. It is only inhibited from differentially spinning by gravitational, magnetic and viscous coupling through the outer core. The rate that Earth's inner core rotates relative to the mantle and crust has been debated for decades. Nonrotational processes, including internal deformation and flow in the outer core, have also been proposed to explain observed seismic changes. The observed changes thus far have been so inconsistent and weak as to hamper convincing interpretation.

I’ll first extensively review the history, then examine waves backscattered from within the inner core, which can more robustly evaluate rotation, from two nuclear tests 3 years apart in Novaya Zemlya, Russia. We have extended our previous analysis of these explosions using precise station corrections and the full Large Aperture Seismic Array and an additional pair of US explosions in the Aleutians, thus revealing how the time shifts depend on slowness and lag time and halving our already turgid rotation rate estimate. Our derived ~0.07°/year inner core super-rotation rate from 1969 to 1974 is more robust, more tightly constrained and slower than most previous estimates and may require interesting reinterpretations of localized signals generally interpreted as inner core rotation. We plan to further refine the analysis of LASA and Hi-net and use more explosions and earthquakes to derive more spatial estimations of the inner core rotation and map the scatterers that enable them.

Presenting Author: Wei Wang

Authors