Geophysicists from ETH Zurich have shown that every wave of a magnitude 3.9 earthquake is recorded in a fiber optic network noise suppression system. This method could enable low-cost earthquake and tsunami early warning systems to be implemented.
Seismic monitoring in less developed countries
While rich countries like Switzerland have a dense network of earthquake monitoring stations, less developed countries and deep in the world’s oceans do not.
Poorer regions lack the money for the necessary number of sensors, while the oceans require complex systems capable of reliably measuring minute pressure changes at depths of thousands of meters and transmitting data signals to the surface.
Secondary use of data for noise suppression
Scientists from the Geophysical Institute of ETH Zurich, in cooperation with the Swiss Federal Institute of Metrology (METAS), have discovered an amazing and inexpensive method that allows accurate measurement of earthquakes even at the bottom of the earth. ocean and in less developed countries.
” We use a function that is already performed by the existing optical infrastructure: we obtain vibration data from an active noise suppression system, which aims to increase signal accuracy in optical data communication “, explains geophysics professor Andreas Fichtner. Simply store active noise cancellation data and evaluate it – no additional equipment or expensive infrastructure required.
To understand how active phase noise cancellation (PNC) can measure seismic shocks, it’s useful to compare it to noise cancellation systems in today’s high-end headphones, which almost completely eliminate noise for the user. These headphones are equipped with microphones that pick up external noise. This signal is inverted and then fed into audio signals in near real time. The inverted phase signal cancels the external noise one by one, making it inaudible.
In the PNC optical data communication system, the “ambient noise» in an optical fiber is determined by comparing the originally transmitted signal with the partial signal that is reflected by the receiver. The difference between the two signals then indicates the interference to which the light signal was exposed on its way through the optical fiber. As with noise cancellation in headphones, this interference can be canceled by using a suitable anti-signal.
The deformations cause minimal changes in frequency
In optical data transmission, “noise” occurs when optical fibers are disturbed by mere micrometers. This occurs in response to deformations of the earth’s surface due to earthquakes, water waves, air pressure differences and human activity. Each deformation slightly shortens or lengthens the fiber. This results in the so-called photoelastic effect, which causes the speed of light in the fiber to fluctuate very slightly.
Changes in fiber length and variations in the speed of light slightly change the frequency of the light signal. This phenomenon has been known for several years and has already been used in special instruments for measuring vibrations.
Exact correspondence with the Swiss Seismological Service
These changes may be minute, but they provide an extremely clear picture of the vibrations that fiber optic cables are subjected to during the observation period. ” Using the PNC optical link between Basel and the atomic clock site at METAS in Bern, we were able to follow in detail each wave of the magnitude 3.9 earthquake in Alsace. “, explains Andreas Fichtner. ” But even better, the earthquake model based on our data also matched the measurements made by the Swiss Seismological Service very closely. »
This near-exact match shows that PNC data can be used to determine earthquake location, depth, and magnitude with a high degree of accuracy. ” This is of particular interest for comprehensive tsunami warnings or for measuring earthquakes in less developed areas of the world », Designates the physics professor.
ETH funding for independent research
For Fichtner, the story of the development of a new method is also exemplary. The idea arose from a discussion between researchers from ETH and a specialist from METAS. Once the ETH-METAS team recognized the potential of PNC data, they quickly implemented the idea.
” For surprising science to emerge, funding must be available for research activities that do not pursue a predetermined goal ” he said. “ ETH is ideal for this type of project. Unlike many other universities, here I have unlimited funding as a researcher. »
Synthetic
This new method of monitoring earthquakes using fiber optic networks could revolutionize the way we monitor and respond to earthquakes, especially in less developed areas and oceans. Using existing noise suppression data, researchers can obtain accurate earthquake information without the need for additional equipment or expensive infrastructure.
For better understanding
What is noise suppression in fiber optic networks?
It is a feature of existing fiber optic infrastructure that helps increase signal accuracy in optical data communications. It is capable of recording vibrations caused by earthquakes.
By storing and evaluating active noise cancellation data, researchers can obtain accurate earthquake information without the need for additional equipment or expensive infrastructure.
What is active phase noise cancellation (PNC)?
PNC is a method used to measure seismic shaking. It works similar to the noise-canceling systems in high-end headphones, canceling the “noise» or external vibrations.
What causes “noise” in optical data transmission?
THE”noise» is caused by the disruption of optical fibers by mere micrometers. This occurs in response to deformations of the earth’s surface due to earthquakes, water waves, air pressure differences and human activity.
What is the potential of this new method?
PNC data can be used to determine the location, depth, and magnitude of an earthquake with a high degree of accuracy. This could be particularly useful for comprehensive tsunami warnings or for measuring earthquakes in less developed areas of the world.
The main lesson
| Learning |
|---|
| 1. Fiber optic networks can pick up waves from a 3.9 earthquake. |
| 2. This method could enable low-cost earthquake and tsunami early warning systems to be implemented. |
| 3. Active noise cancellation data can be used to obtain accurate earthquake information. |
| 4. Active phase noise cancellation (PNC) can measure seismic shaking. |
| 5. Optical fibers are disrupted by mere micrometers in response to deformations of the Earth’s surface. |
| 6. PNC data can be used to determine the location, depth, and magnitude of an earthquake with a high degree of accuracy. |
| 7. This method could be particularly useful for comprehensive tsunami warning or for measuring earthquakes in less developed areas of the world. |
| 8. The idea for this new method came from a discussion between researchers from ETH and a specialist from METAS. |
| 9. ETH researchers have unlimited funding for research. |
| 10. This discovery could have major implications for disaster prevention and public safety in the future. |
Reference
Noe S, Husmann D, Müller N, et al. Long-range fiber-optic earthquake sensing using active phase noise cancellation. SciRep 13, 13983 (2023). doi: external page10.1038/s41598-023-41161-xcall_made
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