Seismic hemispheric asymmetry induced by Earth's inner core decentering
In a first approximation the Earth's interior has an isotropic structure with a spherical symmetry. Over the last decades the geophysical observations have revealed, at different spatial scales, the existence of several perturbations from this basic structure. Some of them are situated in the n...
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Main Authors | , |
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Format | Journal Article |
Language | English |
Published |
04.11.2011
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Subjects | |
Online Access | Get full text |
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Summary: | In a first approximation the Earth's interior has an isotropic structure with
a spherical symmetry. Over the last decades the geophysical observations have
revealed, at different spatial scales, the existence of several perturbations
from this basic structure. Some of them are situated in the neighborhood of the
inner core boundary (ICB). One of the best documented perturbations is the
asymmetry at the top of the inner core (ATIC) characterized by faster seismic
wave velocity in the eastern hemisphere than in the western hemisphere. All
existing explanations are based on a hemispheric variation of the material
properties near ICB inside the inner core. Using numerical simulations of the
seismic ray propagation, we show that the ATIC can be explained as well by the
displacement of the inner core towards east in the equatorial plane tens of
kilometers from the Earth's center, without modifying the spherical symmetry in
the upper inner core. The hypothesis of a displaced inner core is also
sustained by other observed hemispheric asymmetries at the top of the inner
core and at the bottom of the outer core. A displaced inner core would have
major implications for many mechanical, thermal, and magnetic phenomena in the
Earth's interior. |
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DOI: | 10.48550/arxiv.1111.1121 |