Tekla Perry writes: Researchers at Stanford have demonstrated that they can use ordinary, underground fiber optic cables to monitor for earthquakes, by using innate impurities in the fiber as virtual sensors. "People didn't believe this would work," said one of the researchers. "They always assumed that an uncoupled optical fiber would generate too much signal noise to be useful." They plan a larger test installation in 2018. Their biggest challenge, they say, will not be perfecting the algorithms but rather convincing telcos to allow the technology to piggyback on existing telecommunications lines. Meanwhile, the same data is being used for an art project that visualizes the activity of pedestrians, bicycles, cars, and fountains on the surface above the cables.