Seismologists know very well what a hard task it is to detect shear waves propagating through the inner core of the Earth. These signals are so weakly present in the earthquake records, that are often considered below the observational threshold. I have worked closely with Thanh-Son Pham, Xiaolong Ma, and Hrvoje Tkalčić to push forward our observational capabilities and use the similarity of noisy signals (3-10hrs seismic records after large earthquakes) to detect several spectacularly clear shear waves via the global coda-correlation wavefield. We estimate the **absolute shear-wave speed in the inner core**, and we find the inner core is less rigid than previously thought. Our new observation requires a re-assessment of the inner core composition, including the abundance of light elements, atomic properties and stable crystallographic phases of iron at high pressure and temperature conditions!
Are you interested? You can read more here: https://rdcu.be/djS4i