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BRAINIAC

Lessons from a portable earthquake machine

Network for Earthquake Engineering Simulation

The “T-Rex,” a mobile shaker truck

During a live broadcast in the midst of an earthquake in 2011, an announcer for MLB Television made an interesting quip: “Did you know that most of Manhattan is built on landfill…not on granite, and if there were, like, an 8.0 earthquake, then parts of Manhattan would just, just, disintegrate.”

It drove home an important point about earthquake preparedness: No matter how much we beef up building codes, our cites are only as stable as the ground they rest on.

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In that spirit, this summer engineers at the University of Texas, Austin, presented research on soil “improvement” as an earthquake mitigation strategy. The engineers, Kenneth Stokoe and Brady Cox, studied a series of earthquakes that struck Christchurch, New Zealand, in 2010-2011. Those quakes were especially destructive because they caused the “liquefaction” of the soil beneath the city. Christchurch sits on loose, wet soil that, when stirred up by the quake, turned into something like a thick fluid, creating a rolling foundation that undermined most of the city’s buildings.

Stokoe and Cox wanted to test strategies for strengthening soil against liquefaction, which meant finding ways to simulate earthquakes. For that, they turned — as you might expect — to explosives — but also to a 64,000-pound behemoth known as the “T-Rex.” The T-Rex is a “mobile shaker truck” which uses its heft to jostle the earth in a way that resembles the tremors from shifting tectonic plates. Based on those experiments, the engineers concluded that the best ways to fortify soil are to rapidly compact it, or to install vertical piers and horizontal beams beneath buildings.

The idea of changing the composition of the earth to ward against something as massive as an earthquake sounds a little futile. At the same time, there are other areas — like planting trees to prevent erosion — where we’ve successfully used home remedies to staunch tremendous natural forces. And, if we have the T-Rex on our side, maybe we have what it takes to go head-to-head with an earthquake after all.

Kevin Hartnett is a writer in South Carolina. He can be reached at kshartnett18@gmail.com.
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