SAN FRANCISCO – Earthquake cloaks, or huge arrays of precisely drilled holes and trenches in the ground, could — at least in theory — protect important structures like nuclear power plants from powerful seismic waves, researchers say.
The array of holes, drilled at specific angles and depths, would extend sometimes hundreds of feet and scatter earthquake waves like pinballs, according to the scientists.
The idea is still highly speculative, requires a large amount of space that might be impractical, and has not been tested in the ground, but if it works, it could theoretically be used to protect expensive infrastructure that cannot be seismically retrofitted, such as oil pipelines, Vladimir Liberman, a physicist at the Massachusetts Institute of Technology Lincoln Laboratory, said here Thursday (Dec. 15) at the annual meeting of the American Geophysical Union. [Image Gallery: This Millennium’s Destructive Earthquakes]
Protecting vulnerable structures
In places like Oklahoma, oil and gas production has caused swarms of man-made earthquakes, meaning expensive infrastructure such as oil pipelines are now in vulnerable locations. In other areas, nuclear power plants are vulnerable to strong earthquakes. Sometimes, this infrastructure can’t actually be physically modified to make it more resistant to earthquakes, Liberman said.
But what if seismic waves could be deflected before they reach critical infrastructure? To see if there was another way to protect these structures, Liberman and his colleagues created a 3D simulation where they modeled the ground in tiny, three-dimensional cubes, or chunks that varied in size. The model then incorporated drilled holes of varying sizes and orientations, forming a kind of underground zigzag shape. They modeled seismic waves coming from different orientations and found that in computer simulations at least, their setup could deflect a large amount of the energy coming from earthquake waves, Liberman said.
Next, they created a tabletop mockup of the ground using a small block of plastic fitted with tiny accelerometers and drilled with lots and lots of holes in precise orientations, then subjected them to mock seismic waves. The plastic had the right set of physical parameters, such as shear wave velocity and viscosity, to mimic ground-based seismic waves. Similar to their model predictions, the mockup deflected the incoming waves. Based on these experiments, the team thinks its earthquake-cloaking method could reduce the impact from a magnitude-7.0 quake to a magnitude 5.0 or even lower, Liberman said.