"The peculiar structure remained hidden until now as previous studies collected data with less volumetric coverage of the outer core by observing waves that were typically confined within one hour after the origin times of large earthquakes," Tkalčić explained.
"Our findings are interesting because this low velocity within the liquid core implies that we have a high concentration of light chemical elements in these regions that would cause the seismic waves to slow down," Tkalčić said.
"We were able to achieve much better volumetric coverage because we studied the reverberating waves for many hours after large earthquakes," he added.
"We don't know the exact thickness of the doughnut, but we inferred that it reaches a few hundred kilometers beneath the core-mantle boundary," said study coauthor and ANU geophysicist Hrvoje Tkalčić in a statement.
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