Secrets of Earth’s inner core revealed by large quakes

Innermost core seismic waves behave differently from exterior section seismic waves.

According to a research that was released in Nature Communications this week1, the reverberations from earthquakes as they bounce back and forth through the planet's center have disclosed new information about the structure of the inner core.

There has been growing proof for several decades that the planet's solid inner core is made up of different layers2, 3, but little is known about the layers' characteristics.

Researchers used a number of seismometers to study how seismic waves are bent as they travel through the solid mass of iron nickel at Earth's core in order to better understand the innercore's structure. Hrvoje Tkali, a geophysicist at the Australian National University in Canberra, Australia, and a co-author, claims that the earth oscillates like a bell following a significant earthquake, and not just for hours but for days.

Researchers captured waves near to the earthquake's initial epicenter and at the antipode, which is the exact opposite location on Earth's surface, in order to identify these oscillations. They were able to examine the various passages through the center of the Earth as a result. According to co-author Thanh-Son Pham, a postdoctoral associate at the Australian National University, "it's like a ping-pong ball that's moving back and forth." The seismometers captured up to five bounces from a single incident. Each reverberation takes about twenty minutes to travel from one half of the globe to the other.

Built-in dimensions

Each of the initial tremors had a magnitude higher than six, but as the waves traveled through the Earth's interior, they became increasingly weakened. To create a more accurate representation of the distortion coming from the deepest center, the researchers used a method known as "stacking," in which they merged the waveforms from a single occurrence.

They discovered that the waves behaved differently in the innermost inner core than in the outward portion; this core is thought to be approximately 650 kilometers thick. In the core's deepest region, waves slowed down in one direction, while waves in the outer stratum slowed down in a different direction. It simply means that the iron crystals, which are prevalent in the inner core, are likely arranged differently than they are in the inner core's exterior shell, according to Tkali.

The research is significant, according to geophysicist Vernon Cormier of the University of Connecticut in Storrs, because it provides an extremely challenging assessment of the innermost region of the Earth. To determine the wave speed in the extremely deep core of the Earth, Cormier explains that it is necessary to locate seismic waves that have been captured at a great distance and are relatively weak in amplitude.

Although the method is frequently employed in the discovery of resources, it is not frequently applied in geophysics.

The most recent discovery will aid in understanding how Earth's solid inner core developed and what impact it may have had on the magnetic field. This process is believed to have begun between 600 million and 1.5 billion years ago.