Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

Tau.Neutrino said:

Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

Interesting. Gravitational wave sensers make incredibly accurate seismometers.

Tau.Neutrino said:

Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

“The scientists sent pulses of laser light through an optical fibre, which was part of a 15 kilometer cable deployed in 1994 within the telecommunication network on Reykjanes peninsula, SW Island, crossing a well-known geological fault zone in the rift between Eurasian and American tectonic plates. The light signal was analyzed and compared to datasets from a dense network of seismographs. The results amazed even experts: Our measurements revealed structural features in the underground with unprecedented resolution and yielded signals equaling data points every four meters.”

I was not expecting it to be that good. It continually amazes me how good the measurement of the Doppler shift of light can be.

“The method is not new in other applications, it is used for years in boreholes for reservoir monitoring, the team is the first worldwide to conduct such measurements for seismological objectives, and with such a long cable. Their current study not only shows well-known faults and volcanic dykes. The scientists also found a previously unknown fault below the ground surface.

Superb.

“Furthermore, the team measured subsurface deformation taking place over a period of several minutes.”

That’s needed, urgently. The northern part of the Indian Ocean tsunami, a region more than 100 km long, was not detected on seismographs because it happened slowly over a long period of time. If the new detectors could fix that!

“We only need one strand of a modern fibre-optic line”

How? How can they get localisation from that?

mollwollfumble said:

“We only need one strand of a modern fibre-optic line”

How? How can they get localisation from that?

> distributed fibre-optic sensing uses the entire length of an optical fibre as a sensing element allowing a marked densification of spatial sampling down to the metre scale over a distance of tens of kilometres. A passing seismic wave disturbs the sub-surface, locally stretching and compressing the ground; a buried fibre-optic cable is therefore stretched and compressed as well. Fibre-optic sensors measure the response of the optical fibre to the external forces applied to it. This can be done in a variety of ways, but in general the principle involves sending a pulsed coherent optical laser signal propagating along the fibre and measuring the naturally backscattered light. The time-of-flight of the laser signal and its backscattered component are recorded and converted into a distance value using the speed of light and refractive index of the fibre. The phase of Rayleigh backscattered light along an optical fibre is well suited for monitoring dynamic strain changes, with a high spatial and high temporal resolution. Sensitivities down to the nano-strain are achieved with current technologies.

Hell that’s good. Backscatter of a nanosecond pulse, I hadn’t thought of that. Like radar and ultrasound of babies, but with one crucial improvement. In radar, the return signal strength drops as the fourth power of distance. In an optic fibre seismometer the return signal strength is independent of distance, allowing an incredibly large increase in range for small signal strength.

How well does it cope with communications signals multiplexing down the same fibre? Would they have to switch other communications off in order to get it to work?

Reading further, the optic fibre cable in Iceland detected an earthquake in Indonesia, perfectly.

When compared to conventional seismometers, the optic fibre has much more background noise. Not clear why. But for stronger signals gives an exact match to the conventional seismometers.

> We identify signals generated from a large variety of both anthropogenic and natural sources (0.05 Hz up to >100 Hz). High frequency signals (1–100 Hz) are mostly generated by anthropogenic sources, such as passing cars, fluid circulating in pipes of nearby geothermal power stations, hammer shots on the ground, people walking, and distant active explosion shots. In addition, we detected local earthquakes (0.5–20 Hz) associated with the seismic activity of the Mid-Atlantic Ridge.

Not a word in the article about multiplexing.

But I can already see six or so deep sea applications, from wave height forecasts to tracking humpbacks. Including more reliable tsunami forecasts. Even if it can’t be multiplexed with communications, it could still be used on retired undersea cables (there’s one joining Perth to Jakarta for instance) and could even be effectively used on undersea cables that have already been accidentally severed.

mollwollfumble said:

Reading further, the optic fibre cable in Iceland detected an earthquake in Indonesia, perfectly.

When compared to conventional seismometers, the optic fibre has much more background noise. Not clear why. But for stronger signals gives an exact match to the conventional seismometers.

> We identify signals generated from a large variety of both anthropogenic and natural sources (0.05 Hz up to >100 Hz). High frequency signals (1–100 Hz) are mostly generated by anthropogenic sources, such as passing cars, fluid circulating in pipes of nearby geothermal power stations, hammer shots on the ground, people walking, and distant active explosion shots. In addition, we detected local earthquakes (0.5–20 Hz) associated with the seismic activity of the Mid-Atlantic Ridge.

Not a word in the article about multiplexing.

But I can already see six or so deep sea applications, from wave height forecasts to tracking humpbacks. Including more reliable tsunami forecasts. Even if it can’t be multiplexed with communications, it could still be used on retired undersea cables (there’s one joining Perth to Jakarta for instance) and could even be effectively used on undersea cables that have already been accidentally severed.

Would it be useful for detecting sinkholes?

Tau.Neutrino said:

mollwollfumble said:

Reading further, the optic fibre cable in Iceland detected an earthquake in Indonesia, perfectly.

When compared to conventional seismometers, the optic fibre has much more background noise. Not clear why. But for stronger signals gives an exact match to the conventional seismometers.

> We identify signals generated from a large variety of both anthropogenic and natural sources (0.05 Hz up to >100 Hz). High frequency signals (1–100 Hz) are mostly generated by anthropogenic sources, such as passing cars, fluid circulating in pipes of nearby geothermal power stations, hammer shots on the ground, people walking, and distant active explosion shots. In addition, we detected local earthquakes (0.5–20 Hz) associated with the seismic activity of the Mid-Atlantic Ridge.

Not a word in the article about multiplexing.

But I can already see six or so deep sea applications, from wave height forecasts to tracking humpbacks. Including more reliable tsunami forecasts. Even if it can’t be multiplexed with communications, it could still be used on retired undersea cables (there’s one joining Perth to Jakarta for instance) and could even be effectively used on undersea cables that have already been accidentally severed.

Would it be useful for detecting sinkholes?

I think so.

Tau.Neutrino said:

Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

Haven’t read it yet, but that sounds really interesting.

The Rev Dodgson said:

Tau.Neutrino said:

Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

Haven’t read it yet, but that sounds really interesting.

They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

I wonder which Island.

sibeen said:

The Rev Dodgson said:

Tau.Neutrino said:

Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

Haven’t read it yet, but that sounds really interesting.

They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

I wonder which Island.

They probably meant Island UK.

What with Brexit and everything. :)

sibeen said:

The Rev Dodgson said:

Tau.Neutrino said:

Using fibre-optic cables to detect earthquakes

Fibre-optic cables can be used to detect earthquakes and other ground movements. The data cables can also pick up seismic signals from hammer shots, passing cars or wave movements in the ocean. This is the result of a study appearing in the journal Nature Communications on July 3 2018. The main authors are Philippe Jousset and Thomas Reinsch from GFZ German Research Centre for Geosciences. They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

Read more at: https://phys.org/news/2018-07-fibre-optic-cables-earthquakes.html#jCp

Haven’t read it yet, but that sounds really interesting.

They carried out the investigation together with colleagues from Island, UK, Berlin, Germany, and Potsdam, Germany.

I wonder which Island.

Laputa. The island also called Aire.

On undersea cables that are no longer in use. A controversy.

https://www.theguardian.com/sustainable-business/2016/dec/14/ocean-pollution-cable-waste-technology-reuse-recycling-circular-economy-crs-holland

when technology is superseded or a company ceases to trade, what happens to the cables and their copper, aluminium, steel and plastic?

94% of unused cables and 72,000 repeaters are abandoned on the seabed, containing materials worth billions of dollars.

It is like the Wild West in the middle of the ocean. There are millions of kilometres of cables on that ocean floor.

Since 2009 his vessel has reeled in almost 20,000km of defunct cable, worth – he reckons – some $27m.

I hope that some are left for use as earthquake detectors.

sort of a progression of optical time domain reflectometry

digging a few splinters out with a sterilized needle, then hit them with metho, while reading this…..

http://lunainc.com/wp-content/uploads/2016/01/37_Kreger_DSS2015_DynamicRSSensingWithOFDR.pdf

transition said:

digging a few splinters out with a sterilized needle, then hit them with metho, while reading this…..

http://lunainc.com/wp-content/uploads/2016/01/37_Kreger_DSS2015_DynamicRSSensingWithOFDR.pdf

you had a bit of a shake over your way last week didn’t you transition?

transition said:

digging a few splinters out with a sterilized needle, then hit them with metho, while reading this…..

http://lunainc.com/wp-content/uploads/2016/01/37_Kreger_DSS2015_DynamicRSSensingWithOFDR.pdf

Ouch.

Nice paper.

“The same algorithm, applied to successive segments along an unbonded single mode fiber, is an effective means of monitoring the spatial distribution of optical phase perturbations caused by vibration and acoustic wave propagation in the fiber. We will discuss tradeoffs between scan speed, scan duration, range, spatial resolution, vibration sensitivity and vibration frequency range.”

“Analysis of the distributed Rayleigh scatter pattern with Optical Frequency Domain Reflectometry (OFDR) is a well-established method for measuring distributed strain, temperature and 3-dimensional shape with high-spatial resolutions and moderate measurement lengths. There is a trade-off between laser sweep rate and the maximum sensor length that may be interrogated for a given data acquisition rate.”

I hadn’t thought of that. For a 10 km cable, the time delay due to the speed of light is 67 microseconds. For 100 km that’s 0.67 milliseconds. For 1000 km it’s 6.7 milliseconds. Two samples are needed to sample a vibration. So that gives maximum frequency of detection at 7.5 kHz, 750 kHz and 75 Hz.

Humpback whales sing from 30 Hz to 8 kHz. Slight problem with detection there. Earthquake p-waves and s-waves are 0.1 to 2 Hz, no problem there. Ocean wave noise frequency near 0.2 Hz. Ship noise continuum from 20 Hz to 10 kHz with spikes at about 20 and 100 Hz.

New word for the day microbarom

Fibre-optic transmission of 4000 km made possible by ultra-low-noise optical amplifiers

Researchers from Chalmers University of Technology, Sweden, and Tallinn University of Technology, Estonia, have demonstrated a 4000 kilometre fibre-optical transmission link using ultra low-noise, phase-sensitive optical amplifiers. This is a reach improvement of almost six times what is possible when using conventional optical amplifiers. The results are published in Nature Communications.

Read more at: https://phys.org/news/2018-07-fibre-optic-transmission-km-ultra-low-noise-optical.html#jCp