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Rotation and Structure of the Inner Core Illuminated by Repetitive Ancient Nuclear Tests

Session: Back to the Future: Innovative New Research with Legacy Seismic Data [Poster]

Type: Poster

Date: 4/19/2021

Presentation Time: 11:30 AM Pacific

Description: 

We are continuing to examine waves backscattered from within the inner core, which can robustly evaluate rotation and locate fine-scale structural heterogeneities. The rate that Earth's inner core (IC) rotates relative to the mantle has been debated for decades. Non-rotational processes, including internal deformation and flow in the outer core, have also been proposed to explain observed seismic changes. Delineating and interpreting internal IC structure has proven challenging.

We look at three pairs of nuclear tests that are one to three years apart, which are a subset of the 73 globally distributed events recorded on the superb LASA array in Montana, summarized by Wang & Vidale (this meeting). The waves follow after PKiKP, in the subsequent 250s, scattered during two pairs of large nuclear tests in Novaya Zemlya, Russia, one in 1971 and 1974, the other in 1973 and 1974, and a pair in 1969 and 1971 in Amchitka Island, Alaska. We are extending our previous analysis of these explosions using precise station corrections, the full Large Aperture Seismic Array, more sophisticated trace selection based on correlation between the pair of events, and knowledge of which arrivals changed over the years.

We confirm the rate of 0.07°/year inner core super-rotation derived from 1971 to 1974. For the rest of the results, come to the presentation to see what’s new.

Presenting Author: John E. Vidale

Student Presenter: No

Authors