L. Xu G. L. Choy V.F. Cormier 1998 <div class=""><div class="article-section__content en main"><p>Broadband velocity waveforms of PKIKP in the distance range 150° to 180° are inverted for inner core attenuation. A mean<span>&nbsp;</span><i>Q</i>_α<span>&nbsp;</span>of 244 is determined at 1 Hz from 8 polar and 9 equatorial paths. The scatter in measured<span>&nbsp;</span><i>Q</i>⁻¹<span>&nbsp;</span>exceeds individual error estimates, suggesting significant variation in attenuation with path. These results are interpreted by (1) viscoelasticity, in which the relaxation spectrum has a low-frequency corner near or slightly above the frequency band of short-period body waves, and by (2) stratigraphic (scattering) attenuation, in which attenuation and pulse broadening are caused by the interference of scattered multiples in a velocity structure having rapid fluctuations along a PKIKP path. In the scattering interpretation, PKIKP attenuation is only weakly affected by the intrinsic shear attenuation measured in the free-oscillation band. Instead, its frequency dependence, path variations, and fluctuations are all explained by scattering attenuation in a heterogeneous fabric resulting from solidification texturing of intrinsically anisotropic iron. The requisite fabric may consist of either single or ordered groups of crystals with P velocity differences of at least 5% and as much as 12% between two crystallographic axes at scale lengths of 0.5 to 2 km in the direction parallel to the axis of rotation and longer in the cylindrically radial direction, perpendicular to the axis of rotation.</p></div></div> application/pdf 10.1029/1998GL900074 en American Geophysical Union Seismic attenuation of the inner core: Viscoelastic or stratigraphic? article