Planet's internal rotation

This topic is a subject of active research in geophysical community and was exploited in a recent science-fiction motion picture The Core (although the scientific facts in the movie were misrepresented to enhance entertainment). A differential rotation of the inner core with respect to the rest of the mantle was first suggested from numerical simulations of the geodynamo. Since then, seismological studies aiming to detect differential rotation of the inner core using temporal changes in seismic waveforms were controversial and often criticised. One reason for scrutinizing seismological results was inadequate precision to resolve small temporal changes in inner core properties.

However, after the turn of the millennium, earthquake doublets (repetitive earthquakes that are much less subjected to uncertainties due to possible errors in source parameter determination and structure in the mantle) have been used to confirm the differential rotation of the inner core. At the same time, the results from normal modes of the Earth were in odds with a significant differential rotation. We have recently discovered that the differential rotation of the inner core with respect to the mantle is variable in time, which reconciled the old discrepancy in the results from the earthquake doublets and normal modes studies. We found that the inner core accelerated and decelerated more in recent years, but more data are needed to confirm this observation.

This project is twofold: we will explore a unique dataset from the Australian seismic stations in a search for new doublets, and we will collect and explore a global dataset of normal modes to approach inner core rotational dynamics from an independent prospective. A highly motivated student with a background in geophysics, physics, astronomy or mathematics will find the project challenging and satisfying.

Please contact the supervisor directly at Hrvoje.Tkalcic@anu.edu.au for more information.

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