Looking inside the Earth

Defects found in rocks below the Earth's surface have a major impact on the transmission of seismic waves, such as those caused by earthquakes, researchers at The Australian National University have discovered. Professor Ian Jackson, from the Research School of Earth Sciences, part of the ANU College of Physical and Mathematical Sciences, said the team's research allows us to better understand the way seismic waves travel through the mantle deep below the Earth's surface. "We found that defects, known as 'dislocations', in the structures of mantle rocks slow down the passage of seismic waves through the mantle. This new information will help us better interpret seismological models of the Earth's internal structure," Professor Jackson said. "These defects have long been considered responsible for the motions of the Earth's mantle, which have facilitated the movement of tectonic plates over millions of years. This is the first systematic study of their influence over the much shorter timescales of seismic waves. "The rocks of the Earth's mantle behave differently at different time scales.