The Earth’s solid inner core grows from the solidification of the liquid
outer core. The solidification process releases latent heat and expels
light elements, providing driving forces for the outer core convection
and the geodynamo which generates the Earth’s magnetic field.
Thus, the information of the Earth’s inner core boundary is
important for our understanding of the thermo-compositional state of the Earth’s core.
Localized Mushy ICB
Localized mushy zone at the Earth’s inner core boundary beneath southwest Okhotsk Sea.
(a) PKiKP-PcP travel time residuals, plotted at the PKiKP bouncing points at the ICB, which was excited by seismic source (red star) and recorded by Hi-net stations (black triangles). Positive and negative PKiKP-PcP travel time residuals are denoted by circles and triangles, respectively, with the size of symbols proportional to the absolute value of residuals. (b) Compressional velocity profile of the best-fitting model across the ICB (red line) represented by two parameters: d the thickness of the layer and δVP percentage compressional velocity jump of the top layer with respect to PREM velocity jump at ICB, along with PREM (black line). (c) Synthetic seismograms for a series of mushy ICB models (red traces, labeled accordingly with two model parameters: d and δVP) and for PREM (bottom black trace). (d) Comparisons of stacked observed PKiKP waveforms (blue traces), which sample the ICB region beneath southwest Okhotsk Sea and synthetic seismograms (red traces) of the best-fitting models. The number of waveforms used in each stacking is labeled at the right of each trace, while the thickness d and percentage compressional velocity jump of the top layer δVP of the best-fitting models are labeled above the red traces.