The constant, rumbling, teeth-gritting traffic on Highway 99 might actually be good for something. Researchers at Caltech have figured out a way to use vibrations from passing cars to see how much water sits directly beneath the ground’s surface. In a new paper, researchers used seismic waves from traffic noise coupled with unused fiber optic cables underground in a new method to determine how much moisture there is in the top 20 meters of soil.
It’s a level of detail that hasn’t been achieved by other methods of underground detection, according to the researchers. Researchers are able to make use of unused fiber optic cable fibers and convert it into a dense array of seismic sensors to get detailed data on moisture content. The seismic vibrations react to moisture in the shallow ground, slowing down when they hit water.
The level of detail is significantly greater than conventional methods, said Yan Yang, co-author of the study. That’s because researchers can use the fiber optic cable as proxy sensors every eight meters. Traditional sensors are usually spaced hundreds of meters apart, said Yang.
Because of the distance of traditional sensing, changes in moisture can only be detected at much deeper levels, where groundwater lies. “In this technique, because they’re very close, they can sense much shallower regions, which I would say, was very difficult to sense before,” said Xiaojing (Ruby) Fu, contributor to the study. The area of soil between the surface and g.