French researchers have revealed a groundbreaking experiment that could one day shield cities from earthquakes.

the team were able to prove their theory that energy can be routed away from 'quite zones' which could be the most vulnerable parts of cities.

The team say that although their work is at a very early stage, it shows the theory could be used to protect cities.

The seismic metamaterial experiment from Ménard company. The three dashed perimeters account for the location of sensors [measuring the three components of wave velocity (green area on this photograph)], seismic metamaterial [5 m deep self-stable holes of diameter 0.32 m with center-to-center spacing of 1.73 m (blue area)], and rotating source (a vibrating probe set on a crane) with a horizontal displacement of 0.014 m generating an elastic wave at frequency 50 Hz.

HOW IT WORKS The technique is rather like the one used to 'cloak' an object and make it invisible by bending light of specific frequencies around the target.

In theory, the same principles might be used to deflect incoming seismic waves, the team believed. As they expected, sound resonated through the array according to the properties of acoustics, refracting around the boreholes in curved patterns. A precisely tuned array of boreholes around a city or a nuclear power plant that resonate at the frequencies characteristic of quakes could thus dampen the vibrations and shield objects.

In the experiment, the researchers dug a grid of cylindrical holes five meters deep in the soil, then used seismographic sensors to monitor how force propagated through the array.

As they expected, sound resonated through the array according to the properties of acoustics, refracting around the boreholes in curved patterns.

'Materials engineered at the micro- and nanometer scales have had a tremendous and lasting impact in photonics and phononics,' the team wrote in the journal Physical Review Letters.

'At much larger scales, natural soils civil engineered at decimeter to meter scales may interact with seismic waves when the global properties of the medium are modified, or alternatively thanks to a seismic metamaterial constituted of a mesh of vertical empty inclusions bored in the initial soil.'

The hope is that, given the right array and frequency, civil engineers can use this technique to refract earthquakes around cities entirely, creating a kind of central 'quiet zone' safe from the huge amounts of energy unleashed.



'Here, we show the experimental results of a seismic test carried out using seismic waves generated by a monochromatic vibrocompaction probe,' the team say.

'Measurements of the particles’ velocities show a modification of the seismic energy distribution in the presence of the metamaterial in agreement with numerical simulations using an approximate plate model.



'For complex natural materials such as soils, this large-scale experiment was needed to show the practical feasibility of seismic metamaterials and to stress their importance for applications in civil engineering.'

Researchers hope the study could lead to techniques for protecting cities from earthquakes

The team say their experiment was a success.



'We anticipate this experiment to be a starting point for smart devices for anthropic and natural vibrations.

However, as Scientific American says, there are still issues, as all that force has to go somewhere:

'The trick will be to find a way to absorb the massive energy of a major earthquake — or find a better place to send it.'



