Seismological evidence for differential rotation of the Earth's inner core

@article{Song1996SeismologicalEF,
  title={Seismological evidence for differential rotation of the Earth's inner core},
  author={Xiaodong Song and Paul G. Richards},
  journal={Nature},
  year={1996},
  volume={382},
  pages={221-224}
}
The travel times of seismic waves that traverse the Earth's inner core show a small but systematic variation over the past three decades. This variation is best explained by a rotation of the inner core that moves the symmetry axis of its known seismic anisotropy. The inferred rotation rate is on the order of 1° per year faster than the daily rotation of the mantle and crust. 

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

Earth’s inner core rotates at a different rate than the mantle, and discrepancies exist between rotation rates derived from geophysical observations and geodynamical simulations. An inverse analysis

Seismological Constraints on the Structure of the Earth's Core

Our knowledge of the Earth’s core has improved dramatically since its discovery, and this chapter attempts to provide a review of the current understanding as constrained by seismological

Geophysics: Latest spin on the core

During the 1990s evidence has emerged from seismic data that the Earth's inner core may be rotating slightly faster than the mantle and crust. Estimates of the rate have been as high as 3° per year.

Equatorial anisotropy in the inner part of Earth’s inner core from autocorrelation of earthquake coda

The speed of seismic waves passing through the Earth’s inner core varies with direction. Analysis of earthquake seismic data suggests that this directional dependence differs between innermost and

Rotation and Magnetism of Earth's Inner Core

Three-dimensional numerical simulations of the geodynamo suggest that a superrotation of Earth's solid inner core relative to the mantle is maintained by magnetic coupling between the inner core and

Is the Rotation Real?

Earth9s interior consists of a mantle, liquid core, and at the very center a solid inner core made of iron. One of the inner core9s most peculiar properties is its anisotropy: Seismic waves travel

Seismological observation of Earth’s oscillating inner core

We investigate the differential rotation of Earth’s inner core relative to the mantle using pairs of precisely located nuclear explosions. We find that the inner core subrotated at least 0.1° from

Slow differential rotation of the Earth's inner core indicated by temporal changes in scattering

Comparing scattered waves recorded in Montana, USA, from two closely located nuclear tests at Novaya Zemlya, USSR, in 1971 and 1974 shows small but coherent changes in scattering which point toward an inner-core differential rotation rate of 0.15° per year—consistent with constraints imposed by the free-oscillation data.

Seismological Studies on the Deep Interiors of the Earth Viewed from the Polar Region

  • M. Kanao
  • Geology
    Polar Seismology - Advances and Impact
  • 2018
Seismological studies on the deep interiors of the Earth (depth range from the mantle to the inner core) viewed from the polar region have an advantage to promote global geosci-ences, such as for

Earth's core: A new twist on inner-core spin

An observed hemispheric structure in the Earth's inner core has been hard to reconcile with evidence that it rotates faster than the mantle. Detection of a shift of the hemisphere boundary that
...

References

SHOWING 1-10 OF 29 REFERENCES

Axi-symmetric Earth models and inner-core anisotropy

Seismic waves passing through the middle of the Earth travel slightly faster in a N – S direction than in an E – W direction. A comparison of travel times for different P-wave phases shows that most

Convection and anisotropy of the inner core

Estimation of the Rayleigh number of the inner core suggests that this region is convecting. The flow pattern is likely to produce crystallographic preferred orientation of the elastically

Support for anisotropy of the Earth's inner core from free oscillations

IN 1983, Poupinet et al.1 observed that compressional seismic waves traversing the inner core along a trajectory parallel to the Earth's rotation axis arrive faster than the same (PKIKP) waves

Rotation of the earth's solid core as a possible cause of declination, drift and reversals of the earth's magnetic field.

Summary Calculations carried out on a simple model (a gyroscope with a triaxial but nearly sphero-symmetrical inertia ellipsoid having weak isotropic frictional coupling with a surrounding hollow

Possible heterogeneity of the Earth's core deduced from PKIKP travel times

The core of the Earth is usually described by spherically-symmetrical velocity models. The core is made of two main spherical layers: the fluid outer core with a radius close to 3,480 km and a

Structure of the inner core inferred from observations of its spheroidal shear modes

Spheroidal modes of elastic-gravitational oscillation that have an energy partition dominated by shear energy in the inner core are called core modes. Recordings from the IDA gravimeter network of an

Viscosity of the earth's core.

A calculation of the viscosity of the core at the boundary of the inner and outer core that supposes that boundary to be a melting transition and uses the Andrade hypothesis sets limits of 3.7 < η <

Stable regions in the Earth's liquid core

Summary. Slow cooling of the whole Earth can be responsible for the convection in the core that is required to generate the magnetic field. Previous studies have assumed the cooling rate to be high

anisotropy of Earth's inner core

In an effort to confirm inner core anisotropy, we conducted a systematic search for PKP ray paths with various angles from the Earth's spin axis. In particular, we studied paths nearly parallel to

Anisotropy of the inner core from differential travel times of the phases PKP and PKIKP

The difference between the travel times of com-pressional waves that turn in the Earth's liquid outer core (PKP-BC) and those that run in the solid inner core (PKIKP-DF) is primarily sensitive to