Researchers at the King Abdullah University of Science and Technology (KAUST) have detailed a new approach for tracking underground environmental changes in real-time — without drilling.
If you want to monitor an underground environment, it's traditional to drill holes into said environment — an approach which is both destructive and time-consuming. An alternative is seismic imaging, in which sound waves are transmitted into the ground at a range of locations and their echoes timed — a non-destructive approach, but one which is too slow to pick on seismic changes in real-time.
"For a conventional seismic experiment," geophysicist Gerard Schuster explains, "you need many different angular views to accurately estimate the properties of each substructure, which demands many hours to deploy and excite seismic sources over hundreds of different locations."
The solution: A new approach which uses phase differences between signals to reduce the number of audio sources required for a high-resolution scan. "This approach requires much less effort," Schuster claims. "Taking the time differences between the phases allows you to answer questions about the hardness and softness of geology with just a few experiments instead of hundreds."
To prove the concept, Schuster and colleagues monitored a sand dune before, during, and after the injection of 12 tons of water — taking a snapshot of the environment every two minutes. "Our three-dimensional simulations of the experiments convinced us that what we saw wasn’t a false reading," says Schuster. "The initial impact of these findings can be useful for environmental engineers who require rapid and inexpensive monitoring of the subsurface — for example, real-time imaging of leaky dams, or efficient Martian or lunar seismic surveys."
The team's paper has been published under open-access terms in the journal Scientific Reports.