Who would think that drilling a few holes could stop an earthquake? Kate Ravilious writes about the ambitions of physicist Sébastien Guenneau in NewScientist (23 July 2016, paywall):
But in 2001, French seismologist Philippe Guéguen realised that getting buildings to sway could have unexpected benefits. He was studying the effect on Mexico City of a magnitude 7.4 quake that hit it in September 1995. While various parts of the city should have responded in the same way, some neighbourhoods shook for nearly twice as long as others. Softer sediments wobble more than solid rock, but underlying geology wasn’t enough to account for the discrepancy. Instead, it turned out that tall buildings were creating secondary waves in the ground around them, prolonging the shaking but muting the original surface waves. This suggested that the swaying high-rise towers were redistributing the earthquake energy, and providing some protection.
The idea that the waves themselves could be modified, rather than simply withstood, turned earthquake engineering on its head, says Guéguen, who is based at the Institute of Earth Sciences in Grenoble. The key is controlling the way in which the ground responds to incoming waves.
Guenneau had a surprising idea for how this could be achieved. While simply drilling holes in the soil may not seem like it would have much of an impact, he knew that the principle on which it was based had already achieved the impossible.
A small-scale test nearly worked to perfection, with only the small problem that rather redirecting the energy in another direction, or harmlessly dissipating it, the energy was reflected. They are now working on an improvement.
I have a couple of thoughts.
- Rather than redirect or dissipate, how about capturing that energy?
- On a deeper level, how does this disturb the overall system? Is it predictable, or are we setting ourselves up for something bigger? I can’t imagine what, but I do worry about ad hoc fixes that result in bigger problems down the road. Chalk that up to a few disasters of my own in which a fix for one problem lead to larger, unexpected problems somewhere else. I’m not saying a computer program is the same as a natural system … just something to think about.
In a sidebar, another scientist is investigating a similar system for mitigating tsunamis, inspired by the 2004 disaster.
