Scientists may have discovered the origin of mysterious seismic waves in the Earth’s mantle

According to a new study published in the scientific journal Advancing Earth and Space Sciences (AGU Advance), a group of researchers managed to understand a little better the mysterious reaction that occurs as a result of the Earth’s seismic activities. These waves, known as PKP precursor seismic signals, represent a major puzzle in the study of the planet’s seismic waves.

Scientists explained that regions of the planet’s lower mantle scatter incoming seismic signals, but they return as PKP waves and have different speeds than the initial detections.

The big mystery is that researchers have yet to discover the origin of this PKP that precedes the seismic signals. In new research, a team of geophysicists discusses the possible origin of this strange seismic energy.

Because seismic waves travel twice through the Earth’s mantle and are often reflected by the inner layers of the Earth’s mantle, some of them turn into PKP precursors. As the researchers explained in an official statement, PKP precursors may be associated with ‘ultra-low velocity zones’ (ULVZs) in Earth’s mantleIt lies beneath North America and the western Pacific.

“These are some of the most unusual features that have been discovered on the planet. We legitimately don’t know what they are. But one thing we do know is that they appear to be accreting beneath hotspot volcanoes. They appear to be the root of all these mantle plumes that give rise to hotspot volcanoes,” said Michael Thorne, lead author of the study and professor of geology and geophysics at the University of Utah.

PKP seismic waves leading edge

In a widespread situation, seismic waves begin to propagate when the tremors of an earthquake spread into the earth’s interior; Most of these waves follow a normal path, but the PKP precursors are dispersed and have different properties from normal seismic signals.

They pass through the Earth’s mantle twice, once before and once after the Earth’s liquid outer core, which is exactly why the origins of PKP signals have been so difficult to discover.

Seismic waves are widely used by scientists to better understand the Earth’s interior; the origin of PKP signals was discovered thanks to the tremors caused by various earthquakes.

Using a new seismic array method and data collected from 58 recent earthquakes, the team identified the likely origin of the PKP precursors: They may have originated in the boundary between the liquid outer core and the mantle, a region known as the ‘core-mantle boundary’, located 2,900 kilometres below the Earth’s surface.

“I can place virtual sensors anywhere on the Earth’s surface, and that tells me what the seismogram should look like for an earthquake at that location. And we can compare that to the actual recordings that we have. Now we can estimate where the energy is coming from,” Thorne said.

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