Friday, July 31, 2009

'Invisibility Cloak' May Protect Buildings Against Earthquakes

Researchers at the University of Liverpool in the United kingdom have developed a new technology, which has the ability to 'cloak' or protect buildings and large structures from earthquakes.

The term 'invisibility cloak' is used because the technology effectively makes a building 'invisible' to the seismic activity in the event of an earthquake or tremor.

Basically, there are two types of seismic waves produced when an earthquake occurs - body waves and surface waves. Body waves travel through the earth, while surface waves travel across the surface of the earth.

The new cloaking technology controls the path of surface waves, which causes the most damage to surface structures such as buildings. Depending on the strength of an earthquake or tremor, the surface waves are usually responsible for the most substantial loss and destruction during or after the earthquake.

The new technology involves using concentric rings made of plastic, which may be fitted to the Earth’s surface. These concentric rings are used to divert surface waves during an earthquake. The waves traveling through the 'cloak' of concentric rings are compressed into small fluctuations of pressure and density by controlling the stiffness and elasticity of the rings. This causes the waves to pass smoothly into the material. The interesting part of this is that the path of the surface waves may be made into the shape of an arc, in order to direct the waves outside the protective 'cloak'.

By installing these types of concentric rings into the foundations of buildings and larger structures, the technology may be able to make a building almost invisible to earthquakes...or to put it in better terms - almost invisible to the surface shock waves that pass through the surrounding area.

Sebastien Guenneau, from the University’s Department of Mathematics, Stefan Enoch and Mohamed Farhat from the Fresnel Institute (CNRS) in Marseilles explained that they are able to 'tune' the cloak to the differing frequencies of incoming waves. A pair of rings is installed for each small frequency range, which then basically disperses the effects of each frequency range.

Sebastien Guenneau says the waves are then directed outside the cloak, and return to their previous size. He also added that the work has enormous potential for offering protection in densely populated areas of the world most at risk of from earthquakes. Their challenge is now to turn the theory into a practical application - and at the moment, experiments re being conducted on a small scale.

If we understand it correctly, this technology makes a building 'invisible' to seismic activity by allowing shock waves to pass through the area, without actually having any effect on the building itself.

The University of Liverpool is a member of the Russel Group of research-intensive institutions in the United Kingdom, which attracts various collaborative and contract research commissions, both nationally and internationally.


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