Cost-effective method: Swiss researchers turn fiber optic network into earthquake sensor

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This cost-effective method allows earthquakes to be measured accurately on the ocean floor or in countries that do not have the money for a dense enough measurement network, ETH Zurich announced on Thursday.

According to the university, a technology called Active Phase Noise Canceling (PNC) was used in fiber optic cables. This works largely similar to noise cancellation on headphones. Microphones record outside noise and feed the opposing signal practically in real time. This ensures that outside sounds cannot be heard.

“Noise” in glass fibers that transmit light signals is caused by the fibers slightly deforming due to movements of the earth’s surface. This leads to an effect called the photoelastic effect, which causes the speed of light in the fiber to fluctuate minimally. This changes the frequency of the light signals by a very small factor, which is then corrected by the PNC.

Researchers can read earthquakes from this PNC data. As ETH Zurich says, data just needs to be saved. According to the university, this requires neither additional equipment nor expensive infrastructure.

The researchers tested the method on 123 kilometers of fiber optic cable between Basel and Bern during a 3.9 magnitude earthquake. As can be seen from the data published in the journal “Scientific Reports”, they were able to understand each wave of the earthquake in detail. The modeling of the earthquake corresponded extremely precisely to the measurements of the Swiss Seismological Service.

This precise match shows that PNC data can be used to determine both the location and depth and strength of an earthquake with a high degree of accuracy, according to ETH.

(SDA)

Source : Blick