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Seismic Invisibility Cloak

We're used to seeing concentric rings in rippling water. Some seismologists think plastic concentric rings might be handy for protecting buildings from earthquake damage. But what happens to nearby buildings if surface waves continue on their way at full force?

Hemera/Thinkstock

You may think of water or sound when considering the topic of waves, but earthquakes also produce waves, classified by geologists as body and surface waves. The former travel rapidly through Earth's interior. The latter travel more slowly through the upper crust and include a subset of waves -- known as Rayleigh waves -- that move the ground vertically. This up-and-down motion causes most of the shaking and damage associated with an earthquake.

Now imagine if you could interrupt the transmission of some seismic waves. Might it be possible to deflect the energy or reroute it around urban areas? Some scientists think so, and they've dubbed their solution the "seismic invisibility cloak" for its ability to render a building invisible to surface waves. Engineers believe they can fashion the "cloak" out of 100 concentric plastic rings buried beneath the foundation of a building [source: Barras]. As seismic waves approach, they enter the rings at one end and become contained within the system. Harnessed within the "cloak," the waves can't impart their energy to the structure above. They simply pass around the building's foundation and emerge on the other side, where they exit the rings and resume their long-distance journey. A French team tested the concept in 2013.

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