Underwater web cables can detect offshore earthquakes

Discovering movement within the ocean

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Fibre-optic cables are good for quick downloads – and for detecting earthquakes.

Nathaniel Lindsey on the College of California, Berkeley, and his colleagues quickly turned 20 kilometres of present underwater fibre-optic cables right into a row of seismic sensors alongside the ground of the Pacific Ocean.

The researchers recorded a 3.5-magnitude earthquake and found a brand new fault system off the coast of California.


Fibre-optic cables transmit info within the type of gentle. An intensive underwater community of those cables connects all of the continents besides Antarctica and transmits telecommunications information, together with phone and web site visitors.

The researchers used a way referred to as distributed acoustic sensing, which works by sending pulses of sunshine by the cable and analysing the sunshine that returns to detect slight actions.

“For those who begin shifting a sure portion of the fibre as a result of there’s some seismic wave propagating, you’ll be capable of see that seismic wave pressure on the cable,” says Lindsey.

Throughout a four-day experiment, the workforce occurred to measure an earthquake, in addition to the scattering of the earthquake’s wave fronts by beforehand unknown faults – fractures in Earth’s crust – in Monterey Bay.

We nonetheless don’t know the places of all of the faults on Earth, significantly in hard-to-measure places resembling beneath cities or on the ocean ground.

Distributed acoustic sensing might be used to show different present cables that aren’t in use into offshore seismic sensors to map underwater faults and earthquakes extra extensively, says Lindsey.

“The variety of sensors we have now on the ocean ground on the west coast of North America might be counted on one hand,” he says. “There may be a variety of cable within the ocean relative to the quantity of sensors that we presently have.”

The cables on this examine had been positioned in a shallow coastal space, with a most depth of round 100 metres. In future, the researchers plan to check the approach in areas the place the ocean ground is far deeper or extra sloped.

Journal reference: Science, 10.1126/science.aay5881

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