Researchers from Australia have finally managed to confirm our planet’s core is solid, although it is not as scientists predicted in earlier studies.
The inner core of our planet is solid but softer than previously believed, according to a study published today in Australia that hopes to help understand how our planet was formed.
Expert in seismography Hrvoje Tkalčic and Ph.D. candidate Than-Son Pham, of the Australian National University (ANU), zeroed in on a low amplitude ‘J-phase’ seismic wave that passes through the planet’s core, allowing them to finally put constraints on its solidity.
“If our results are correct, the internal core of the planet shares some similar elastic properties with gold and platinum,” Tkalčic said in a statement from the ANU.
“The Earth’s core is like a time capsule. If we understand it well, we will understand how the planet was formed and how it evolves, “he added.
Inner core shear waves are so tiny it is impossible to observe them directly.
In fact, detecting them has been considered the “Holy Grail” of global seismology since scientists first predicted the inner core was solid in the 1930s and 40s.
This is why experts from ANU came up with a revolutionary method.
The scientists’ correlation wavefield method observed the similarities between the signals at two receivers after a major earthquake, rather than the direct wave arrivals. Scientist shave been using a similar technique by the same team to measure the thickness of Antarctic Ice.
“We’re throwing away the first three hours of the seismogram and what we’re looking at is between three and 10 hours after a large earthquake happens. We want to get rid of the big signals,”. Dr Tkalčic said.
“Using a global network of stations, we take every single receiver pair and every single large earthquake — that’s many combinations — and we measure the similarity between the seismograms. That’s called cross correlation, or the measure of similarity. From those similarities we construct a global correlogram — a sort of fingerprint of the Earth.”
This research was published in Science.