Geoscientists are using telecom ‘dark fibres’ to map Earth’s innards

Offline telecom cables called “dark fibres” can be used to sense underground seismic waves. Geophysicists are increasingly using such signals to study aspects of Earth’s subsurface, including hidden sources of geothermal energy and earthquake hazards.

“If a large earthquake happens on the fibre on which we are speaking, the frequencies in my voice would be slightly distorted,” Andreas Fichtner at ETH Zurich in Switzerland told New Scientist on a video call.

He is referring to…