Researchers Map 300 Feet Underground With 458 Thunderquakes and 2,100 Fiber-Optic Sensors
Updated
Updated · Yahoo! Voices · Aug 21
Researchers Map 300 Feet Underground With 458 Thunderquakes and 2,100 Fiber-Optic Sensors
3 articles · Updated · Yahoo! Voices · Aug 21
Summary
A 2-mile fiber-optic cable in State College captured 458 clear thunderquakes over two years, letting researchers reconstruct an X-ray-like image of the subsurface to about 300 feet without drilling.
Using distributed acoustic sensing, the team turned the cable into more than 2,100 closely spaced vibration sensors and tracked air-coupled Rayleigh waves, whose frequency-dependent speeds reveal underground structure.
The survey identified four weak zones where seismic waves slowed sharply; two match areas of active ground subsidence seen in satellite radar, consistent with fractures, voids or water in karst rock.
Because karst terrain covers about 20% of continental land and affects nearly a quarter of the global population, the method could help flag sinkhole, groundwater and foundation risks more cheaply than conventional surveys.
The researchers say the approach could extend beyond thunderstorms to sonic booms, eruptions and meteor airbursts, and may even inform future subsurface studies on Titan.