is inner core translation a good model ?
DESCRIPTION
Is inner core translation a good model ?. Vernon Cormier, Lizzie Day, Zack Geballe, Marine Lasbleis , Mohammad Youssof , Han Yue. Does the inner core grows layer by layer?. Does it convect ?. Deguen , 2012. Summary of s eismic features. SLOW isotropic velocity - PowerPoint PPT PresentationTRANSCRIPT
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Is inner core translation a good model?
Vernon Cormier, Lizzie Day, Zack Geballe, Marine Lasbleis,
Mohammad Youssof, Han Yue
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Does the inner core grows layer by layer?
Does it convect?
Deguen, 2012
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Modified from a figure by Jessica Irving
Inner inner core?
EastWest
• FAST isotropic velocity • More attenuating (low Q) • Less anisotropic
• SLOW isotropic velocity•Less attenuation (high Q)• More anisotropic
Summary of seismic features
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Waszek & Deuss, JGR, 2012
Hemispheres of P-wave travel time
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T-dependent viscoelasticity is not the cause
East
West
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8.5 mol % Si< 8.8 mol % Si
Composition is an unlikely cause
Cottaar and Buffet (2012)Alfe et al. (2002)
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Translation: a type of convectionSlow Fast
Monnereau et al., Science, 2010
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Age distribution in a translating inner core
300 km 500 kmAge (Ma)
0 15075
0 km 100 km
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Average age sampled by imaginary seismic data set
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Age domain size seismic properties
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Model explains the Vp hemispheres!
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1 elasticity model fits, 5 do not
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Tuned parameter #2: Domains grow to ~ λseismic/2π
Calvet and Margerin, 2008
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Q from model < observed Q
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Other seismic features
Inner inner core?
EastWest
Modified from a figure by Jessica Irving
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Future tests• Try to explain innermost inner core with a
textured polycrystalline scattering model• Test a spectrum of iron elasticity models• Map Vp in different frequency bins• Map Q
Conclusion:Rigid translation is consistent with observed hemispherical variation in Vp provided that: (1) domains grow to approximately λSeismic/2π , (2) the iron alloy making up the inner core has relatively high
elastic anisotropy