Geodynamical models and seismic observations suggest that the Earth’s solid inner core rotates at a different rate than the mantle. However, discrepancies exist in rotation rate estimates based on seismic waves produced by earthquakes. Here we investigate the inherent assumption of a constant rotation rate using earthquake doublets—repeating earthquakes that produce similar waveforms. We detect that the rotation rate of the Earth’s inner core with respect to the mantle varies with time. We perform an inverse analysis of 7 doublets observed at the College station, Alaska, as well as 17 previously reported doublets, and reconstruct a history of differential inner-core rotation between 1961 and 2007. We find that the observed doublets are consistent with a model of an inner core with an average differential rotation rate of 0.25–0.48° yr−1 and decadal fluctuations of the order of 1° yr−1 around the mean. The decadal fluctuations explain discrepancies between previous core rotation models and are in concordance with recent geodynamical simulations.
Your institute does not have access to this article
Open Access articles citing this article.
Surveys in Geophysics Open Access 30 September 2021
Nature Communications Open Access 08 May 2020
Scientific Reports Open Access 14 April 2020
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Glatzmaier, G. H. & Roberts, P. H. Rotation and magnetism of Earth’s inner core. Science 274, 1887–1891 (1996).
Gubbins, D. Rotation of the inner core. J. Geophys. Res. 86, 11695–11699 (1981).
Kuang, W. & Bloxham, J. An Earth-like numerical dynamo model. Nature 389, 371–374 (1997).
Olson, P. Probing Earth’s dynamo. Nature 389, 337–338 (1997).
Aurnou, J. M. & Olson, P. Control of inner core rotation by electromagnetic, gravitational and mechanical torques. Phys. Earth Planet. Int. 117, 111–121 (2000).
Song, X. & Richards, P. Seismological evidence for differential rotation of the Earth’s inner core. Nature 382, 221–224 (1996).
Su, W-J., Dziewonski, A. M. & Jeanloz, R. Planet within a planet: Rotation of the inner core of Earth. Science 274, 1883–1887 (1996).
Su, W. J. & Dziewonski, A. M. A local anomaly in the inner core. Eos Trans. AGU (Spring Meet. Suppl.) 79, S218 (1998).
Souriau, A., Roudil, P. & Moynot, B. Inner core differential rotation: Facts and artefacts. Geophys. Res. Lett. 24, 2103–2106 (1997).
Souriau, A. in Deep Earth Structure—The Earth’s Cores, in Treatise on Geophysics Vol. 1 (ed. Schubert, G.) 655–693 (Elsevier, 2007).
Tkalčić, H. & Kennett, B. L. N. Core structure and heterogeneity: A seismological perspective. Austral. J. Earth Sci. 55, 419–431 (2008).
Creager, K. Inner core rotation rate from small-scale heterogeneity and time-varying travel times. Science 278, 1284–1288 (1997).
Souriau, A. New seismological constraints on differential rotation of the inner core from Novaya Zemlya events recorded at DRV, Antarctica. Geophys. J. Int. 134, F1–F5 (1998).
Song, X. D. Joint inversion for inner core rotation, inner core anisotropy, and mantle heterogeneity. J. Geophys. Res. 105, 7931–7943 (2000).
Laske, G. & Masters, G. Earth’s Core: Dynamics, Structure, Rotation Vol. 31 (eds Dehant, V. et al.) 5–21 (Geodymanics Series, American Geophysical Union, 2003).
Jault, D., Gire, C. & Le Mouel, J-L. Westward drift, core motions and exchanges of angular momentum between core and mantle. Nature 333, 353–356 (1988).
Jackson, A., Bloxham, J. & Gubbins, D. Dynamics of Earth’s Deep Interior and Earth Rotation Vol. 72 (eds Le Mouël, J-L., Smylie, D., & Herring, T.) 97–107 (Geophysical Monograph Series, American Geophysical Union, 1993).
Aubert, J. & Dumberry, M. Steady and fluctuating inner core rotation in numerical geodynamo models. Geophys. J. Int 184, 162–170 (2011).
Poupinet, G., Souriau, A. & Coutant, O. The existence of an inner core super-rotation questioned by teleseismic doublets. Phys. Earth Planet. Int. 118, 77–88 (2000).
Li, A. & Richards, P. G. Using earthquake doublets to study inner core rotation and seismicity catalog precision. G-cubed 4, 1–23 (2003).
Bondár, I. & Storchak, D. Improved location procedure at the International Seismological Centre. Geophys. J. Int. 186, 1220–1244 (2011).
Zhang, J., Song, X. D., Li, Y., Richards, P. G. & Sun, X. Inner core differential motion confirmed by earthquake waveform doublets. Science 309, 1357–1360 (2005).
Collier, J. D. & Hellfrich, G. Estimate of inner core rotation rate from United Kingdom regional seismic network data and consequences for inner core dynamical behaviour. Earth Planet. Sci. Lett. 193, 523–537 (2001).
Song, X. & Poupinet, G. Inner core rotation from event-pair analysis. Earth Planet Sci. Lett. 261, 259–266 (2007).
Lindner, D., Song, X., Ma, P. & Christensen, D. H. Inner core rotation and its variability from nonparametric modeling. J. Geophys. Res. 115, B04307 (2010).
Denison, D. G. T., Holmes, C., Mallick, B. & Smith, A. F. M. Bayesian Methods for Nonlinear Classification and Regression (Wiley, 2002).
Geyer, C. & Møller, J. Simulation procedures and likelihood inference for spatial point processes. Scand. J. Statist. 21, 359–373 (1974).
Green, P. Reversible jump MCMC computation and Bayesian models selection. Biometrika 82, 711 (1995).
Green, P. Trans-dimensional Markov chain Monte Carlo. Highly Struct. Stocha. Syst. 27, 179–198 (2003).
Bodin, T., Sambridge, M., Tkalčić, H., Gallagher, K. & Arroucau, P. Transdimensional inversion of receiver functions and surface wave dispersion. J. Geophys. Res. 117, B02301 (2012).
Bodin, T. & Sambridge, M. Seismic tomography with the reversible jump algorithm. Geophys. J. Int. 178, 1411–1436 (2009).
Sambridge, M., Bodin, T., Gallagher, K & Tkalčić, H. Transdimensional inference in the geosciences. Phil. Trans. R. Soc. A 371, 20110547 (2013).
Vidale, J. E. & Earle, P. S. Evidence for inner core rotation from possible changes with time in PKP coda. Geophys. Res. Lett. 32, L01309 (2005).
Dumberry, M. Geodynamic constraints on the steady and time dependent inner core axial rotation. Geophys. J. Int. 170, 886–895 (2007).
Gillet, N., Jault, D., Canet, E. & Fournier, A. Fast torsional waves and strong magnetic field within the Earth’s core. Nature 465, 74–77 (2010).
Dumberry, M. & Mound, J. Inner core–mantle gravitational locking and the super-rotation of the inner core. Geophys. J. Int. 181, 806–817 (2010).
Wen, L. Localized temporal change of the Earth’s inner core boundary. Science 314, 967–970 (2006).
Cao, A., Masson, Y. & Romanowicz, B. Short wavelength topography on the inner-core boundary. Proc. Natl Acad. Sci. USA 104, 31–35 (2007).
Mäkinen, A. M. & Deuss, A. Global seismic body-wave observations of temporal variations in the Earth’s inner core, and implications for its differential rotation. Geophys. J. Int. (2011).
Dumberry, M. Gravitationally driven inner core differential rotation. Earth Planet. Sci. Lett. 297, 387–394 (2010).
Tanaka, S. & Hamaguchi, H. Degree one heterogeneity and hemispherical variation of anisotropy in the inner core from PKP(BC)-PKP(DF) times. J. Geophys. Res. 102, 2925–2938 (1997).
Niu, F. & Wen, L. Hemispherical variations in seismic velocity at the top of the Earth’s inner core. Nature 410, 1081–1084 (2001).
Waszek, L., Irving, J. & Deuss, A. Reconciling the hemispherical structure of Earth’s inner core with its super-rotation. Nature Geosci. 4, 264–267 (2011).
Monnereau, M., Calvet, M., Mergerin, L. & Souriau, A. Loopsided growth of Earth’s inner core. Science 328, 1014–1017 (2010).
Alboussière, Deguen, R. & Melzani, M. Melting-induced stratification above the Earth’s inner core due to convective translation. Nature 466, 744–747 (2010).
We would like to acknowledge X. D. Song and P. G. Richards for making available previously observed and published waveform doublets. The data consist of digitized analogue data (from the WWSSN archive in Lamont) as well as the data available through the IRIS DMC archive. H.T. is grateful to R. Deguen, M. Fang and the colleagues from RSES, ANU for useful discussions.
The authors declare no competing financial interests.
About this article
Cite this article
Tkalčić, H., Young, M., Bodin, T. et al. The shuffling rotation of the Earth’s inner core revealed by earthquake doublets. Nature Geosci 6, 497–502 (2013). https://doi.org/10.1038/ngeo1813
Nature Geoscience (2022)
Surveys in Geophysics (2022)
Nature Communications (2020)
Scientific Reports (2020)