London: Scientists are observing distant earthquakes by `listening` to them to reveal new clues about the top of the earth`s core.
The approach is akin to hearing a conversation across a whispering gallery, such as those in the domes of some large cathedrals.
Using a novel digital processing approach, researchers at the University of Calgary (U-C) analysed faint signals produced by 44 earthquakes. They were able to measure the sound speed at the top of earth`s core with unprecedented accuracy.
Knowledge of the composition and state of this zone is key to unravelling the source of the earth`s magnetic field and the formation of our planet.
"Some scientists have proposed a region of sediment accumulation at the top of the core, or even distinct liquid layers, but this study shows that the outer core is, in fact, well mixed," says professor Dave Eaton at U-C and study co-author.
"This inaccessible region is composed of molten iron, nickel and other as-yet unknown lighter elements such as silicon, sulphur, carbon or oxygen," he added.
To help try and determine the materials that make up the earth`s core, which is 2,891 km below the surface, Eaton and co-author Catrina Alexandrakis, U-C doctoral student, measured the seismic wave speed (speed of sound) at the top of earth`s core, a U-C release said.
"Scientists have to investigate distant earthquakes in deep parts of the earth," Alexandrakis says.
The paper is slated for publication in the May edition of Physics of the Earth and Planetary Interiors.