A recent study by researchers from the Australian National University (ANU) could help us understand how our planet originated.
Associate Professor Hrvoje Tkalčić and PhD Scholar Than-son Phạm are confident that they now have direct evidence that the Earth's inner core is stable.
They have found a way to detect shear waves or "J waves" inside the core ̵
"We found the inner core indeed solid, but we also found it softer than previously thought," said Professor Tkalčić.
"It Turns When our results are right, the inner core shares some similar elastic properties with gold and platinum.The inner core is like a time capsule, if we understand it, we will understand how the planet was shaped and how it does developing. "
Inner nuclear shear waves are so tiny and weak that they can not be directly observed. In fact, their discovery was considered the "holy grail" of global seismology, as scientists for the first time predicted that the inner core was solid in the 1930s and 40s.
The researchers therefore had to develop a creative approach The so-called correlation wave field method examines the similarities between the signals in two receivers after a severe earthquake and not the direct wave arrivals. A similar technique was used by the same team to measure the thickness of Antarctic ice.
"We throw away the first three hours of the seismogram and see three to ten hours after that a big earthquake happened, we want to get rid of the big signals," Dr. Tkalcic.
"With a global network of stations, we take every single pair of receivers and every big earthquake – that's a lot of combinations – and we measure the similarity between the seismograms, that is cross-correlation or the measure of similarity." From these similarities we construct global correlogram – a kind of fingerprint of the earth. "
The study shows that these results can then be used to illustrate the seismograms existence of J-waves and infer the shear wave velocity in the inner core.
While this specific information about shear waves is important, Dr. Tkalčić, which tells this research about the inner core, is even more exciting. Or we still do not know what the exact temperature of the inner core is, how old the inside of the core or how fast it freezes, but with these new advances in global seismology, we are slowly getting there.  "The understanding of the Earth's inner core has direct consequences for the creation and maintenance of Earth's magnetic field, and without this Earth's magnetic field there would be none Life on the Earth's surface. "
The research was published in Science .
The temperature 3,000 kilometers below the earth's surface is much more diverse than previously thought
Hrvoje Tkalčić et al. Scissors properties of the Earth's inner core limited by detection of J-waves in the global correlation wave field, Science (2018). DOI: 10.1126 / science.aau7649