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 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 Waszek & Deuss, JGR, 2012 Hemispheres of P-wave travel time T-dependent viscoelasticity is not the cause East West 8.5 mol % Si < 8.8 mol % Si Composition is an unlikely cause Cottaar and Buffet (2012) Alfe et al. (2002) Translation: a type of convection SlowFast Monnereau et al., Science, 2010 Translation: a type of convection Make figure of isetropes and geotherm to show that latent heat fights convection. Age distribution in a translating inner core 300 km 500 km Age (Ma) km 100 km Average age sampled by imaginary seismic data set Age domain size seismic properties Model explains the Vp hemispheres! 1 elasticity model fits, 5 do not Tuned parameter #2: Domains grow to ~ seismic /2 Calvet and Margerin, 2008 Q from model < observed Q Other seismic features Inner inner core? EastWest Modified from a figure by Jessica Irving 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 Seismic /2, (2) the iron alloy making up the inner core has relatively high elastic anisotropy