Tracking Noises - with Light

Fiber Optics at the Heart of Smart Underground Sensors

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When the wind blows and the trees sway, Adelos can hear the tree roots moving.

The supersensitive acoustic sensor can also hear the movement of gas or oil inside a pipeline - and recognize when the flow has changed.
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Buried 18 inches underground, where it is virtually undetectable by countermeasures, its makers say, Adelos can hear distant vehicles clearly enough to identify what they are and in which direction they're traveling.

Nifty, this makes me wonder if they can incorporate this into seismology measurements. Perhaps they'll be able to utilize this technology to map Calderas or Magma Chambers of suspected active volcanoes. Based on the concept of the technology it doesn't seem all that improbable.