Looking inside the Earth

Apr 23, 2012
Looking inside the Earth
Stuck in Customs on Flickr.

(Phys.org) -- 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 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 , 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. At periods of microseconds to nanoseconds, typical of seismic waves, they are quite rigid. However, over periods of millions of years they lose their rigidity entirely, behaving instead like fluid. Previous research has shown that dislocations contribute to this interesting change in behavior.”

To investigate the impacts of these defects on the passage of seismic waves, the team made synthetic materials in the laboratory to represent the mantle rocks below the surface. They then deformed the synthetic rocks to introduce dislocations into the materials, and tested them with novel techniques at 1-1000 second seismic timescales.

Co-author Dr. John Fitzgerald, also from the Research School of Earth Sciences, said that these findings allow for a better understanding of how the materials below the Earth’s surface transmit seismic waves, such as those associated with earthquakes.

“It tells us that the same defects that allow the long-term movement of the tectonic plates also have an important influence on the way seismic waves travel through the Earth’s mantle. Such insights from the laboratory will help ‘calibrate’ the seismological probe of the Earth’s internal structure – yielding tighter constraints on its thermal regime and long-term evolution,” Dr. Fitzgerald said.

The paper, "Dislocation Damping and Anisotropic Attenuation in the Earth’s Upper Mantle," was published today in Science.

Explore further: NASA balloons begin flying in Antarctica for 2014 campaign

Provided by Australian National University

4.5 /5 (4 votes)

Related Stories

Gradients in the Earth's outermost core

Dec 08, 2010

Evidence that the outermost portion of the Earth’s core is stratified is provided by earthquake data reported by scientists at the University of Bristol this week in Nature.

New explanation for Hawaiian hot spot

May 27, 2011

(PhysOrg.com) -- Scientists in the US have suggested that volcanic activity in Hawaii could be fed by a giant hot rock pool 1,000 kilometers west of the islands and in the Earth’s mantle, rather than ...

A speed gun for the Earth's insides

Oct 27, 2010

(PhysOrg.com) -- Researchers at the University of Bristol reveal today in the journal Nature that they have developed a seismological 'speed gun' for the inside of the Earth. Using this technique they will b ...

Atoms under the mantle

Mar 06, 2007

French CNRS scientists have succeeded in modelling the defects of the earth’s mantle responsible for its deformation. These results, obtained using a novel approach which combines numerical calculus and quantum ...

Quakes unearth Australia's underground past

Jan 10, 2012

(PhysOrg.com) -- Researchers from The Australian National University have used the latest earthquake-measuring technology to image the tectonic plate beneath southeast Australia and reveal for the first time ...

Recommended for you

Scientists make strides in tsunami warning since 2004

8 hours ago

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

9 hours ago

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.