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We Can Measure How Traffic Vibrates the Earth

Special instruments called geophones help researchers distinguish the signatures of big trucks rumbling down the highway and planes taking off

(Henrik Trygg/Corbis)
smithsonian.com

If you’ve ever mistaken a truck idling outside for a minor earthquake, this news will come as no surprise: The vibrations from traffic create seismic waves that ripple through the earth below us. The patterns are so specific that scientists can even measure them and observe what’s happening by monitoring the ground.

"[We] can follow a metro schedule, count aircraft and their acceleration on a runway and even see larger vehicles on a 10-lane highway," two researchers—Nima Riahi and Peter Gerstoft from the Scripps Institution of Oceanography—reported at the 168th Meeting of the Acoustical Society of America

Riahi and Gerstoft used a network of 5,300 geophones spread around Long Beach, Calif. The instruments measure vibrations in the earth, reports Mary Beth Griggs for Popular Science. She writes:

The geophones were originally installed as part of an oil and gas survey in the area, but the scientists figured out that in addition to being able to map out likely locations of resources, the network was also able to pick up on the vibrations caused by human transportation.   

By spacing the geophones every 300 feet, the researchers demonstrated that this kind of monitoring could provide a new way to gather data on traffic, according to a press release. Perhaps that could lead to less headache-inducing commutes?

These rumblings of the earth, at least, are unlikely to leave traces in the geological record—unlike our boreholes or the remnants of underground nuclear explosions. The same cannot be said for the pavement and concrete layers we have put down in order to run our earth-vibrating machines from place to place.

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