Fiber optic cables usually used to carry internet data could also help warn of impending earthquakes, it has been revealed.
Researchers have successfully used an existing fibre-optic communications cable to monitor seismic activity.
It could lead to radical new methods to monitor large areas.
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The scientists found that the cable in Iceland not only recorded seismic signals, but were also able to detect the surrounding faults and other underground geological structures.
The study was led by Philippe Jousset of the German Research Centre for Geosciences in Potsdam.
Jousset and his team set up an experiment in Iceland, where fiber-optic cables were transformed into a series of sensors to record both natural and man-made seismic waves.
Researchers setting up the experiment: They used 15km of fibre-optic cable that had originally been installed between two geothermal power plants in Iceland in 1994.
They used 15km of fibre-optic cable that had originally been installed between two geothermal power plants in Iceland in 1994.
A laser pulse sent down a single fibre of the cable was sufficient to determine whether there were any disturbances along its length.
When the ground, and the cable, was stretched or compressed, the team were able to record it.
The scientists found that the cables not only recorded seismic signals, but were also able to detect the surrounding faults and other underground geological structures.
IS CALIFORNIA AT RISK OF A DEVASTATING MEGAQUAKE?
A recent report from the U.S. Geological Survey has warned the risk of ‘the big one’ hitting California has increased dramatically.
Researchers analysed the latest data from the state’s complex system of active geological faults, as well as new methods for translating these data into earthquake likelihoods.
The estimate for the likelihood that California will experience a magnitude 8 or larger earthquake in the next 30 years has increased from about 4.7% to about 7.0%, they say.
‘We are fortunate that seismic activity in California has been relatively low over the past century,’ said Tom Jordan, Director of the Southern California Earthquake Center and a co-author of the study.
Shown above is the chance of an earthquake across California over the next 30 years
‘But we know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable.’
Seismologist Lucy Jones from the US Geological Survey warned recently that people need to accept the fact catastrophe is imminent, and prepare themselves accordingly.
Dr Jones said our decision to not accept it will only mean more people suffer as scientists warn the ‘Big One’ is now overdue to hit California.
Dr Jones, who is from the US Geological Survey said there are three key reasons why the peril is so frightening – it cannot be seen, it is uncertain and it seems unknowable.
This means people bury their heads in the sand and pretend it won’t happen.
‘Our measurements revealed structural features in the underground with unprecedented resolution and yielded signals equaling data points every four meters’, says Jousset.
‘This is denser than any seismological network worldwide.’
The scientists also found a previously unknown fault, below the ground surface.
They detected local traffic, seismic shaking and even passing pedestrians.
They also picked up a signal from a strong earthquake in Indonesia.
‘We suggest that the networks of fibre-optic telecommunication lines worldwide could be used as seismometers opening a new window for Earth hazard assessment and exploration,’ they wrote in Nature.
The advantages of the new method are enormous, they say, as there are countless fibre-optic cables spanning the globe in the dense telecommunication network beneath megacities with high seismic hazards, such as San Francisco, Mexico City, Tokyo, or Istanbul.
HOW ARE EARTHQUAKES MEASURED?
The magnitude of an earthquake differs from its intensity.
The magnitude of an earthquake refers to the measurement of energy released where the earthquake originated.
Magnitude is calculated based on measurements on seismographs.
The intensity of an earthquake refers to how strong the shaking that is produced by the sensation is.
A 5.3 magnitude earthquake hit the Channel Islands off the coast of southern California on Thursday at 10.30am
According to the United States Geological Survey, ‘intensity is determined from the effects on people, human structures and the natural environment’.
Earthquakes originate below the surface of the earth in a region called the hypocenter.
During an earthquake, one part of a seismograph remains stationary and one part moves with the earth’s surface.
The earthquake is then measured by the difference in the positions of the still and moving parts of the seismograph.
They could provide a cost efficient and widely spread addition to existing seismological measuring devices.
‘We only need one strand of a modern fibre-optic line’, says Charlotte Krawczyk, Director of GFZ’s Geophysics Department.
Future studies are planned to investigate whether deep-sea cables can also be used for seismic measurements.
In an article that accompanied the study, U.S. Geological Survey geophysicist Elizabeth S. Cochran wrote that ‘a revolution in seismic detection technology is underway, capturing unprecedented observations of earthquakes and their impacts.’
She said these sensors could give real-time ground-shaking observations that could improve emergency response after damaging earthquakes, and could also advance our understanding of the physics of earthquakes.
‘I look forward to a time when smoke detectors and smart gas meters, or even perhaps millions of toasters, provide records useful for seismology,’ Cochran said.