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Updated: Jun 13, 2026
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Simulation of the Planetary Interior Differentiation Processes in the Laboratory
Published on: November 15, 2013
Hemispherical anisotropic patterns of the Earth's inner core
Maurizio Mattesini1, Anatoly B Belonoshko, Elisa Buforn
1Departamento de Física de la Tierra, Astronomía y Astrofísica I, Universidad Complutense de Madrid, E-28040 Madrid, Spain. mmattesi@fis.ucm.es
Summary
The Earth's inner core exhibits complex hemispherical anisotropy. Seismic data suggest a body-centered-cubic iron phase, not hexagonal-close-packed iron, is present at the inner core's top.
Area of Science:
- Geophysics
- Seismology
- Mineral Physics
Background:
- The Earth's inner core displays axisymmetric anisotropy, with seismic waves traveling faster along polar paths than equatorial ones.
- Existing models using hexagonal-close-packed iron struggle to explain complex hemispherical anisotropic patterns observed in the solid Earth's core.
- Seismological observations indicate a need for alternative iron phases or structural arrangements.
Purpose of the Study:
- To investigate the underlying cause of the observed hemispherical anisotropy in the Earth's inner core.
- To determine if a body-centered-cubic iron phase can account for seismological data.
- To provide compelling evidence for the composition and structure of the Earth's inner core.
Main Methods:
- Analysis of seismic wave travel-time anomalies.
- Comparison of observed data with theoretical models of iron's crystallographic preferred orientation.
- Modeling the influence of different iron crystal structures (hexagonal-close-packed vs. body-centered-cubic) on seismic anisotropy.
Main Results:
- The collected seismic data align well with the presence of two distinct, anisotropically specular east and west core hemispheres.
- Travel-time anomalies are explained by a lattice-preferred orientation of a body-centered-cubic iron aggregate.
- A fraction of the [111] crystal axes of this body-centered-cubic iron phase are parallel to the Earth's rotation axis.
Conclusions:
- The findings strongly support the presence of a body-centered-cubic iron phase at the top of the Earth's inner core.
- This body-centered-cubic iron structure, with specific crystallographic alignment, successfully explains the observed hemispherical seismic anisotropy.
- The study refines our understanding of the Earth's deep interior composition and structure.
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