Tuesday, April 23, 2024

Fibre Optic Cables Effective Way To Detect Tsunamis

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The innovative method uses fibre optic cables for tsunami detection, providing an alternative to traditional buoys and enabling real-time monitoring of environmental changes.

Locations of the subsea DAS (Distributed Acoustic Sensing) system, DART (Deep-ocean Assessment and Reporting of Tsunamis) observation systems, BPRs (bottom pressure recorders), tide gauge, and two tsunami events. Panel (b) indicated by the blue box in panel (a), shows the precise locations of the DART and tide gauge. Panel (c) zooms in on the red box in panel (b), revealing the water depth and position of the DAS system. Credit: Geophysical Research Letters (2024). DOI: 10.1029/2023GL106767
Locations of the subsea DAS (Distributed Acoustic Sensing) system, DART (Deep-ocean Assessment and Reporting of Tsunamis) observation systems, BPRs (bottom pressure recorders), tide gauge, and two tsunami events. Panel (b) indicated by the blue box in panel (a), shows the precise locations of the DART and tide gauge. Panel (c) zooms in on the red box in panel (b), revealing the water depth and position of the DAS system. Credit: Geophysical Research Letters (2024). DOI: 10.1029/2023GL106767

The Deep-ocean Assessment and Reporting of Tsunamis (DART) system, managed by the National Oceanic and Atmospheric Administration, consists of specialised buoys that monitor tsunamis. Installing each buoy costs around $500,000, with an additional $300,000 required annually for maintenance. With thirty-two detection buoys around the Pacific Ocean, the annual upkeep costs millions of dollars—a necessary expense for safety.

However, University of Michigan and California Institute of Technology researchers have explored a more cost-effective and widespread method for monitoring tsunamis. They’ve employed a technique called distributed acoustic sensing (DAS) to utilise the approximately 1 million miles of fibre optic cables that span ocean floors.

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In the past five years, the team have set up Distributed Acoustic Sensing (DAS) interrogator units in fibre optic telecommunication companies located in Alaska, Japan, Spain, and Lake Ontario, which connect to underwater fibre optic cables. Utilising a device installed in Florence, Oregon, the team successfully detected a tsunami that originated in an island chain nearly 1,300 miles east of the tip of South America.

The researchers are still investigating the specific mechanism through which tsunamis affect fibre optic cables. One possibility is that the pressure-induced deformation from the additional water above the cables could stretch the fibres, altering how photons are refracted. Temperature changes might also have a similar effect, but further research is required to pinpoint the exact impact on the fibres.

The DAS system could provide telecommunication companies with an alternative use for fibre optic cables in the future, as satellites increasingly take over as the primary means of delivering internet services. According to the researchers, the cables could be repurposed for various applications, including military surveillance, boat tracking, measuring internal ocean waves, monitoring ocean temperatures, and researching climate change.

Next, the researchers indicate that software must be developed to interpret data from fibre optic cables for real-time tsunami detection.

Reference: Han Xiao et al, Detection of Earthquake Infragravity and Tsunami Waves With Underwater Distributed Acoustic Sensing, Geophysical Research Letters (2024). DOI: 10.1029/2023GL106767

Nidhi Agarwal
Nidhi Agarwal
Nidhi Agarwal is a journalist at EFY. She is an Electronics and Communication Engineer with over five years of academic experience. Her expertise lies in working with development boards and IoT cloud. She enjoys writing as it enables her to share her knowledge and insights related to electronics, with like-minded techies.

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