Earth Deep Interior

The Earth’s solid inner core grows from the solidification of the liquid outer core. The solidificaiton 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. The information of the Earth’s inner core boundary (ICB) is important for our understanding of the thermo-compositional state of the Earth’s core. We use seismic waves reflected from the Earth’s ICB to study the spatial and temporary changes of ICB.

Seismic discontinuities in the mantle provide critical insight into thermal and compositional states of Earth’s mantle and its dynamics. The 410- and 660-km seismic discontinuities are observed globally, and are generally linked to phase transformations of olivine → wadsleyite and ringwoodite → bridgmanite + ferropericlase. The 520- and 560-km discontinuities are usually less observed and studied, and are caused by phase transformation of wadsleyite → ringwoodite, and exsolution of Ca-pv from garnet. We analyze waveforms of SS precuros recorded by global stations to investigate global variations of the 520- and 560-km discontinuities.