Underwater telecom cables make superb seismic network

phys.org ^ | 11/28/2019 | U C Berkely

[BenLurkin]

In a paper appearing this week in the journal Science, researchers from the University of California, Berkeley, Lawrence Berkeley National Laboratory (Berkeley Lab), Monterey Bay Aquarium Research Institute (MBARI) and Rice University describe an experiment that turned 20 kilometers of undersea fiber-optic cable into the equivalent of 10,000 seismic stations along the ocean floor. During their four-day experiment in Monterey Bay, they recorded a 3.5 magnitude quake and seismic scattering from underwater fault zones.

Their technique, which they had previously tested with fiber-optic cables on land, could provide much-needed data on quakes that occur under the sea, where few seismic stations exist, leaving 70% of Earth's surface without earthquake detectors.

The technique the researchers use is Distributed Acoustic Sensing, which employs a photonic device that sends short pulses of laser light down the cable and detects the backscattering created by strain in the cable that is caused by stretching. With interferometry, they can measure the backscatter every 2 meters (6 feet), effectively turning a 20-kilometer cable into 10,000 individual motion sensors.

[PapaBear3625]

During the underwater test, they were able to measure a broad range of frequencies of seismic waves from a magnitude 3.4 earthquake that occurred 45 kilometers inland near Gilroy, California, and map multiple known and previously unmapped submarine fault zones, part of the San Gregorio Fault system. They also were able to detect steady-state ocean waves—so-called ocean microseisms—as well as storm waves, all of which matched buoy and land seismic measurements.

I wonder how well this system would work to detect passage of submarines, and whether that's the real purpose of the research?

[conservatism_IS_compassion]

Hmmm . . .

[newfreep]

I’ve always wondered why submarines have never cut these cables?

It would certainly be a nightmare to splice the cables back to re-establish connection.

[NYAmerican]

“researchers from the University of California, Berkeley”

From UC Berkeley??? I presume they will find disparities and racism in the Transmission of Undersea data?

[FreedomPoster]

Seems very likely. There’s big money in that sort of research. I saw it with underwater acoustics many years ago.

[Openurmind]

Lol, source aside, it really is kind of cool technology and dual use re-utilization of an existing infrastructure.

[MeneMeneTekelUpharsin]

Can they find Godzilla?

[mosesdapoet]

They should be ab;e to develop a fiber optic system to detect oceanic volcanic activity as well.

[NYAmerican]

Yes, it is interesting. Sounds to me much like the existing fiber optic intrusion sensing fibers security companies string along fences at secure facilities. I’m sure lots of cool stuff comes out of UC Berkeley, too bad they soil their own image with their non stop left wing activism under the cloak of “Higher Education”.

[2001convSVT]

Theoretically, any change in pressure should effect the strain on the fiber optic cable. The difficult part is detecting the very small signals over background noise and pinpointing its location within a worthwhile accuracy.

[Openurmind]

I agree, not much good has come from Berkeley at all, just a whole lot of false propaganda.

[libertylover]

researchers from the University of California, Berkeley

Hmmpt! I can't believe it. Even using "Find on page" I couldn't find a single mention of "Climate Change" or "Global Warming"! Me suspects these researchers have some "splaining" to do with their bosses.