Credit: CC0 Public DomainA new study of Australian National University (ANU) researchers can help us understand how our planet was…
Credit: CC0 Public Domain
A new study of Australian National University (ANU) researchers can help us understand how our planet was formed.
Lecturer Hrvoje Tkalčić and PhD Scholar Than-Son Phạm are convinced that they now have direct evidence that the inner core of the earth is solid.
They came up with a way to detect shear waves or “J waves” in the inner core ̵
1; a type of wave that can only travel through solid objects.
“We found that the inner core is solid, but we also found it smoother than previously thought,” said Professor Tkalčić. “19659005” out – if our results are correct parts the inner core has some similar elastic properties with gold and platinum. The inner core is like a time capsule, if we understand we understand how the planet was formed and how it evolved. “
Internal nucleus waves are so small and weak that they can not be observed directly. Discovering them has actually been regarded as the” sacred degree “of global seismology because researchers predicted the inner core was solid in the 1930’s and 40’s.  So the researchers had to come up with a creative approach.
Their so-called correlation waveform method looks at the similarities between the signals of two receivers after a major earthquake, rather than the direct wave events. A similar technique has been used by the same layer to measure The thickness of ice in Antarctica.
“We are throwing away the first three hours of the seismogram and what we are looking at is between three and 10 hours after a major earthquake happens. We want to get rid of the big signals, says Dr Tkalčic.
“With a global network of stations, we take each recipient pair and every major earthquake – there are many combinations – and we measure the similarity between seismograms. It is called cross-correlation, or the measure of equality. From these similarities we construct a global correlogram – a kind of fingerprint of the earth. “
The study shows that these results can be used to demonstrate the presence of J waves and divert the shear wave velocity into the inner nucleus.
Although this specific information about shear waves is important, Dr. Tkalčić says what this research tells us if the inner core is even more exciting.
“F or we do not know what the internal core’s exact temperature is, what the age of the inner nucleus is, or how fast it solidifies, but with these new advances in global seismology, we slowly come. ” Understanding of the inner core of the earth has direct consequences for the generation and maintenance of the geomagnetic field and without the geomagnetic field there would be no life on the surface of the earth. “
The research has been published in science .
The temperature of 3,000 kilometers below the earth’s surface is much more varied than previously thought
Hrvoje Tkalčić et al. Shear properties of the earth’s inner core limited by a discovery of J waves in global correlation wavefield, Science (2018). DOI: 10.1126 / science.aau7649