Inner core scattering estimates inferred from PKiKP coda waves

Lateral variations in structure and composition with a scale length of about several kilometers are thought to be one of the reasons for strong seismic attenuation in the Earth’s solid inner core. These fine-scale heterogeneities are probably best constrained by scattered coda of body waves pre-critically reflected from the inner core boundary (PKiKP). Here we analyze 9 arrays of sources and receivers to detect weak PKiKP coda on short-period and broadband seismic records in the range of epicentral distances from 6 to 94 degrees. 6 PKiKP bounce points scan the IC surface below Central Asia, 2 – under the Arctic region, and one – under Southeastern Asia. We observe the IC scattered coda in the Hilbert envelope of the PKiKP beam built by linear summation of 1.3 – 5 Hz bandpass frequency filtered vertical records of array channels. Assuming the detected PKiKP codas result from scattering through the volume of the uppermost inner core, we estimate the Qc quality factor by fitting of the observed PKiKP codas with a standard model – the classical method invoked in crust and mantle studies. We find the quality factors are between 400 and 500 with no distinct geographical dependence.