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| Titel |
Flexural anisotropy in the continental lithosphere: How robust are our estimates? |
| VerfasserIn |
Lara Kalnins, Frederik Simons, Jon Kirby, Dong Wang, Sofia Olhede |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108271
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| Publikation (Nr.) |
 EGU/EGU2015-11023.pdf |
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| Zusammenfassung |
| In addition to considering the magnitude and lateral variation of the long-term strength
of the lithosphere, we must also consider its directional variation, its anisotropy.
Many geological materials and processes are themselves anisotropic; this might lead
to a natural expectation of widespread anisotropy in lithosphere strength, which
both modulates and is modulated by many key tectonic processes. Cratons, with
their long, complex geological histories, and orogenic belts, the result of extremely
anisotropy processes, might seem especially likely to show anisotropy in their flexural
rigidity.
The observed coherence between gravity and topography remains the most popular
metric for the analysis of flexural rigidity, and, indeed, it is frequently anisotropic.
However, does this correspond to anisotropy in the actual mechanical strength of
the lithosphere? Using coherence, we should only reject the null hypothesis of
isotropy when there is significant anisotropy in both the observed coherence and the
resulting flexural strength. In addition, the anisotropy should not arise purely from
marginal (in the statistical sense) anisotropy in the topography and gravity data
themselves.
We use wholly isotropic synthetic models to test two common methods for estimating
coherence, multitapers and wavelets, and find widespread spurious anisotropy using both
methods. Using a series of statistical and geophysical tests developed to identify and remove
such spurious directionality, our global reanalysis shows sparse evidence for meaningful
anisotropy in the mechanical strength of the lithosphere. Although the geological argument
for anisotropy in these regions and its role in tectonic cycles remains highly plausible, this
anisotropy has not yet been convincingly verified by any cross-spectral method. |
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