Researchers at Penn State have demonstrated a surprising new use for buried fiber-optic cables: imaging what lies beneath the ground using vibrations created by thunderstorms.
When lightning produces thunder, some of that acoustic energy enters the ground and generates tiny seismic waves, sometimes called “thunderquakes.” Those waves travel differently depending on the materials they pass through, providing clues about underground rock, sediment, fractures and water.
The researchers used a roughly 4-kilometer fiber-optic line beneath Penn State’s campus as a distributed seismic sensor. Over two years, they identified 458 clear thunderquakes and used them to reconstruct parts of the shallow subsurface.
The resulting images revealed four weak underground zones where seismic waves traveled more slowly. Independent boreholes, engineering surveys and other seismic measurements confirmed that those areas contained unusual geological features.
The approach could eventually help with sinkhole detection, groundwater studies, landslide monitoring and infrastructure planning, particularly in areas where fiber-optic networks are already installed.
There are limitations. Thunderstorms are unpredictable and produce far messier seismic signals than controlled surveys, so it isn’t a replacement for conventional geological imaging, but does show that existing communications infrastructure could potentially double as a large-scale sensing network.
The same fiber carrying internet traffic could also help scientists see underground.
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