Scientists use earthquakes to prove that the Earth's core is solid

As no one is on hand to observe the formation of the earth some 4.5 billion years ago, the best we can hope for is to observe the state of the planet today. To discover how our house came into existence. An essential part of this process is to determine whether the inner core of the Earth is a solid mass or some kind of extremely hot liquid mud in motion. Researchers at the Australian National University (ANU) believe they have determined that the core of the Earth is probably solid but somewhat spongy.

The key was to detect the "shear waves" emanating from the nucleus. These are seismic waves that propagate only in solid rocks, but the core waves are so tiny that no one has yet been able to detect them. It was not even clear that there were waves to be detected. This is important because a liquid core would not be able to transmit shear waves. A solid core would be. If you can prove that the shear waves propagate in the nucleus, you have probably proved that they are solid.

Associate Professor Hrvoje Tkalčić and Ph.D. Scholar Than-Son Phạm of UNA has developed a method of waiting for an earthquake. A large. Researchers describe their method of measuring the heart of the Earth as a "wavefield method". After an earthquake, they used sensitive seismic probes to record every little noise. However, they can not start right after the earthquake. It takes about three hours for the major rumble to set in, allowing seismograms to record more subtle signals bouncing inside the Earth. This is very similar to the techniques used to measure the thickness of the Antarctic ice.

The different layers of the Earth, including the crust, the mantle, the outer core and the inner core

The study shows that the seismic maps produced in this post-earthquake window from three to ten o'clock can basically take the fingerprints of the planet. The map shows the presence of shear waves emanating from the center of the planet and also allowed Tkalčić and Phạm to deduce the speed of the waves.

From these data, the researchers think they have determined that the core is really solid. However, it is not a monolithic and immobile mass. The core has elastic properties similar to those of gold and platinum. We still do not know the exact temperature of the nucleus, its age or rate of solidification. However, the new waveform method could help to learn these things in the future.

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