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The shuffling rotation of the Earth’s inner core revealed by earthquake doublets

Abstract

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.

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Figure 1: Newly observed doublet and PKP waves.
Figure 2: Waveform doublets and measurement methods.
Figure 3: Solution model and posterior distribution of the number of nodes.
Figure 4: Inner-core differential rotation rate as a function of time.

References

  1. Glatzmaier, G. H. & Roberts, P. H. Rotation and magnetism of Earth’s inner core. Science 274, 1887–1891 (1996).

    Article  Google Scholar 

  2. Gubbins, D. Rotation of the inner core. J. Geophys. Res. 86, 11695–11699 (1981).

    Article  Google Scholar 

  3. Kuang, W. & Bloxham, J. An Earth-like numerical dynamo model. Nature 389, 371–374 (1997).

    Article  Google Scholar 

  4. Olson, P. Probing Earth’s dynamo. Nature 389, 337–338 (1997).

    Article  Google Scholar 

  5. Aurnou, J. M. & Olson, P. Control of inner core rotation by electromagnetic, gravitational and mechanical torques. Phys. Earth Planet. Int. 117, 111–121 (2000).

    Article  Google Scholar 

  6. Song, X. & Richards, P. Seismological evidence for differential rotation of the Earth’s inner core. Nature 382, 221–224 (1996).

    Article  Google Scholar 

  7. Su, W-J., Dziewonski, A. M. & Jeanloz, R. Planet within a planet: Rotation of the inner core of Earth. Science 274, 1883–1887 (1996).

    Article  Google Scholar 

  8. Su, W. J. & Dziewonski, A. M. A local anomaly in the inner core. Eos Trans. AGU (Spring Meet. Suppl.) 79, S218 (1998).

    Article  Google Scholar 

  9. Souriau, A., Roudil, P. & Moynot, B. Inner core differential rotation: Facts and artefacts. Geophys. Res. Lett. 24, 2103–2106 (1997).

    Article  Google Scholar 

  10. Souriau, A. in Deep Earth Structure—The Earth’s Cores, in Treatise on Geophysics Vol. 1 (ed. Schubert, G.) 655–693 (Elsevier, 2007).

    Book  Google Scholar 

  11. Tkalčić, H. & Kennett, B. L. N. Core structure and heterogeneity: A seismological perspective. Austral. J. Earth Sci. 55, 419–431 (2008).

    Article  Google Scholar 

  12. Creager, K. Inner core rotation rate from small-scale heterogeneity and time-varying travel times. Science 278, 1284–1288 (1997).

    Article  Google Scholar 

  13. 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).

    Article  Google Scholar 

  14. Song, X. D. Joint inversion for inner core rotation, inner core anisotropy, and mantle heterogeneity. J. Geophys. Res. 105, 7931–7943 (2000).

    Article  Google Scholar 

  15. 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).

  16. 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).

    Article  Google Scholar 

  17. 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).

  18. Aubert, J. & Dumberry, M. Steady and fluctuating inner core rotation in numerical geodynamo models. Geophys. J. Int 184, 162–170 (2011).

    Article  Google Scholar 

  19. 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).

    Article  Google Scholar 

  20. Li, A. & Richards, P. G. Using earthquake doublets to study inner core rotation and seismicity catalog precision. G-cubed 4, 1–23 (2003).

    Google Scholar 

  21. Bondár, I. & Storchak, D. Improved location procedure at the International Seismological Centre. Geophys. J. Int. 186, 1220–1244 (2011).

    Article  Google Scholar 

  22. 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).

    Article  Google Scholar 

  23. 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).

    Article  Google Scholar 

  24. Song, X. & Poupinet, G. Inner core rotation from event-pair analysis. Earth Planet Sci. Lett. 261, 259–266 (2007).

    Article  Google Scholar 

  25. Lindner, D., Song, X., Ma, P. & Christensen, D. H. Inner core rotation and its variability from nonparametric modeling. J. Geophys. Res. 115, B04307 (2010).

    Article  Google Scholar 

  26. Denison, D. G. T., Holmes, C., Mallick, B. & Smith, A. F. M. Bayesian Methods for Nonlinear Classification and Regression (Wiley, 2002).

    Google Scholar 

  27. Geyer, C. & Møller, J. Simulation procedures and likelihood inference for spatial point processes. Scand. J. Statist. 21, 359–373 (1974).

    Google Scholar 

  28. Green, P. Reversible jump MCMC computation and Bayesian models selection. Biometrika 82, 711 (1995).

    Article  Google Scholar 

  29. Green, P. Trans-dimensional Markov chain Monte Carlo. Highly Struct. Stocha. Syst. 27, 179–198 (2003).

    Google Scholar 

  30. 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).

    Article  Google Scholar 

  31. Bodin, T. & Sambridge, M. Seismic tomography with the reversible jump algorithm. Geophys. J. Int. 178, 1411–1436 (2009).

    Article  Google Scholar 

  32. Sambridge, M., Bodin, T., Gallagher, K & Tkalčić, H. Transdimensional inference in the geosciences. Phil. Trans. R. Soc. A 371, 20110547 (2013).

    Article  Google Scholar 

  33. 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).

    Article  Google Scholar 

  34. Dumberry, M. Geodynamic constraints on the steady and time dependent inner core axial rotation. Geophys. J. Int. 170, 886–895 (2007).

    Article  Google Scholar 

  35. 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).

    Article  Google Scholar 

  36. Dumberry, M. & Mound, J. Inner core–mantle gravitational locking and the super-rotation of the inner core. Geophys. J. Int. 181, 806–817 (2010).

    Google Scholar 

  37. Wen, L. Localized temporal change of the Earth’s inner core boundary. Science 314, 967–970 (2006).

    Article  Google Scholar 

  38. Cao, A., Masson, Y. & Romanowicz, B. Short wavelength topography on the inner-core boundary. Proc. Natl Acad. Sci. USA 104, 31–35 (2007).

    Article  Google Scholar 

  39. 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).

  40. Dumberry, M. Gravitationally driven inner core differential rotation. Earth Planet. Sci. Lett. 297, 387–394 (2010).

    Article  Google Scholar 

  41. 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).

    Article  Google Scholar 

  42. Niu, F. & Wen, L. Hemispherical variations in seismic velocity at the top of the Earth’s inner core. Nature 410, 1081–1084 (2001).

    Article  Google Scholar 

  43. 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).

    Article  Google Scholar 

  44. Monnereau, M., Calvet, M., Mergerin, L. & Souriau, A. Loopsided growth of Earth’s inner core. Science 328, 1014–1017 (2010).

    Article  Google Scholar 

  45. Alboussière, Deguen, R. & Melzani, M. Melting-induced stratification above the Earth’s inner core due to convective translation. Nature 466, 744–747 (2010).

    Article  Google Scholar 

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Acknowledgements

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.

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Authors and Affiliations

Authors

Contributions

S.N. and H.T. contributed algorithms and methods for doublet search. M.Y., S.N. and H.T. worked together on improving methods for identification of doublets and their measurements. M.Y. performed time measurements and made the waveform figures under the supervision and verification of measurements by H.T. The inversion approach was designed by T.B. based on his PhD thesis supervised by M.S. and discussions with H.T. Synthetic tests were designed by H.T. and T.B., and T.B. contributed figures and supplementary text related to the Bayesian method. H.T. designed the study, wrote the manuscript and produced the figures, which all authors commented on and edited.

Corresponding author

Correspondence to Hrvoje Tkalčić.

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The authors declare no competing financial interests.

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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

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