Alaska Earthquake and Seismic Wave Reflections. Credit: Drew Whitehouse, Son Phạm and Hrvoje Tkalčic.
Not so long ago, our planet had four layers – crust, mantle, outer core and inner core. This division has worked since the 1930s. Now, almost a hundred years later, it increasingly appears that the Earth actually has five layers. In the inner core, most likely, the fifth layer, the innermost core, is hidden, English innermost inner core. It should be a massive ball of metal about 650 kilometers in size that sits in the center of the planet.
Thanh-Son Pham. Credit: ANU.
The existence of the innermost core of the Earth has been speculated for about 20 years. Recently, a pair of seismologists from the Australian National University (ANU), Thanh-Son Pham and Hrvoje Tkalčić, intervened in this matter. By analyzing the seismic waves from the earthquake, they concluded that these waves confirm the presence of the innermost core at the very center of the Earth. As part of the research, they processed data from approximately 200 earthquakes of magnitude 6 and higher that occurred during the last decade.
Hrvoje Tkalčić. Credit: ANU.
According to the researchers, their research represents a new line of evidence that speaks in favor of the existence of the innermost core. They developed a procedure that amplifies the seismic signals recorded by dense networks of seismographs operating at diverse locations on the Earth’s surface. They dealt with seismic waves that pass through the center of the planet during an earthquake.
Such waves bounce back on the opposite side of the Earth, then bounce back to the opposite side, and again and again. Like someone flicking a pinball against a wall. With each such reflection, the waves weaken. In previous studies, researchers typically only recorded a single reflection. Pham and Tkalčić detected a total of five of them for individual earthquakes.
It is a new approach to the study of the Earth’s inner core region. Pham and Tkalčić found that the behavior of seismic waves from various earthquakes as they pass through the inner core indicates the existence of material inside the inner core with properties different from the rest of the inner core. They concluded that this region of the planet, the innermost core, differs in its crystalline structure.
Researchers believe that the existence of the innermost core of the Earth may be related to a fundamental planetary event of a global nature, which at a certain moment in the history of our planet led to a change in the structure of the material in the inner core of the Earth. They believe that further elucidation of the situation around the innermost core will lead to a better understanding of the formation and development of planets.
Video: Using seismic waves as evidence for the inner Earth structure
Literature
Australian National University 22. 2. 2023.
Nature Communications 14: 754.
