Researchers at the Australian National University (ANU) believe they have obtained direct evidence that the inner core of the Earth is solid and shares some similar elastic properties with gold and platinum. To find out, they devised a way to detect cut waves, or "J waves" in the inner core, a type of wave that can only travel through solid objects. The research was published in Science.
The cutting waves of the inner core are so small and weak that they can not be directly observed. In fact, their detection was considered the "Holy Grail" of global seismology as scientists predicted for the first time that the inner core was solid 80 years ago. "The inner core is like a time capsule, if we understand it, we will understand how the planet was formed and how it evolves", says one of the authors of the work, Hrvoje Tkalcic.
The so-called correlation wave field method used by these scientists analyzes the similarities between the signals in two receivers after a major earthquake, rather than the direct wave arrivals. A similar technique was used by the same team to measure the thickness of ice in Antarctica. "We found that the inner core is really solid, but we also found that it's softer than we thought, and if our results are correct, the inner core shares some similar elastic properties with gold and platinum," he says. scientist.
Using a global network of stations, they picked up each pair of receivers and each large earthquake and measured the similarity between the seismograms, in a technique called cross-correlation or the measure of similarity. From these similarities, scientists have constructed a global correlogram, a sort of digital fingerprint of the Earth. "We are discarding the first three hours of the seismogram and what we are seeing is between three and ten hours after a major earthquake occurred, we want to get rid of the big signs," said Tkalcic.
The study shows that these results can be used to demonstrate the existence of J waves and infer the cutting wave velocity in the inner core. While this specific information on cutting waves is important, for Tkalcic what this research tells us about the inner core is even more exciting: "For example, we do not yet know what the exact core core temperature is, the core age internal or the speed with which it solidifies, but with these new advances in global seismology, we are gradually coming ".
Understanding the inner core of the Earth has direct consequences for the generation and maintenance of the geomagnetic field, without which there would be no life on the surface of the Earth.
Beatriz de Vera
This news was originally published on N + 1, a science that is added.
About N + 1: It is the first online scientific and technological publication that allows the total or partial reproduction of its contents through communication, bloggers and influencers, making mention of the text and the link to the web: "This news has it was originally published in the journal N + 1, science that adds: www.nmas1.org ".