'Invisible' Building Design Could Reduce Earthquake Damage

Physicists propose shielding buildings to re-direct vibrations around them.

ByABC News
July 17, 2009, 3:18 PM

July 19, 2009— -- WASHINGTON (ISNS) -- Engineers have been developing earthquake-resistant buildings for years, but a group of physicists now believe it's possible to make an entire building effectively disappear from an earthquake's destructive path, avoiding serious damage.

Inspired by the recent development of novel materials that precisely control the flow of light waves around objects, they've shown that the same ideas can work whether the waves make up light, sound or earthquakes.

Earthquakes are some of the most destructive forces in nature. The waves they produce ripple across the earth's surface, much as water waves travel across the ocean. The waves from earthquakes crumple buildings, bridges, and other structures, causing millions of dollars in damage and often death.

Despite efforts to understand earthquakes and reinforce buildings against them, damage from the shaking ground is nearly impossible to avoid. But that may not be the case for long, say a team of physicists in France and the United Kingdom.

Recently, physicists have been developing better and better invisibility cloaks, which hide an object from sight by causing incoming light waves to bend around the object, and come together behind the object.

Physicists Mohamed Farhat and Stefan Enoch of the Fresnel Institute in Marseille, France, and Sebastien Guenneau of LiverpoolUniversity in England wondered if they could use the same principles to hide an object from the destructive waves produced during an earthquake.

In a paper to be published this week in the journal Physical Review Letters, the three physicists show that the answer may be "yes."

Guenneau said that it's possible to shield an object, even a building, so that an incoming earthquake wave behaves as if the object weren't there. The building in the path of the wave is like a rock in afast-flowing river, he said.

"It's the same picture, the wave pattern, as for a water wave that is propagating in a river, and it's bent smoothly around the rock and will be reconstructed around the rock." The object, or building, is "invisible" to the mechanical waves.