Mechanical Q-Factor in the Earth’s Upper Inner Core Inferred from PKiKP Coda Waves

Abstract—Based on the alpha-shape computer-graphics analysis of coda envelope of the waves from nuclear explosions reflected from the inner core boundary (PKiKP), the estimates of the mechanical Q-factor are obtained for nine reflection regions beneath the Arctic, Central, and Southeast Asia with the average Q = 447 ± 43. The coda formation mechanism can be associated with the heterogeneities in the upper inner core with a characteristic linear size of 1–4 km and variations in P-wave velocity on the order of 1–3%.