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Using fibre optic networks to better detect volcanic activity

Peter Griffin, Editor. 18 January 2022, 10:11 am

The eruption of the Hunga Tonga-Hunga Ha Ľapai volcano 65km north of Nuku'alofa has served as a reminder of the vulnerability of telecommunications infrastructure to natural hazards.

Tonga's undersea cable link to the outside world appears to have been severed as a result of the undersea eruption, which has hampered efforts to ascertain the extent of the tsunami damage to the islands that make up the Kingdom of Tonga.

To make matters worse, the volcanic ash generated by the eruption has settled on satellite dishes, disrupting satellite voice and data communications as well. The CS Reliance, a cable maintenance ship, is en route to the area to undertake repairs, but it could be up to two weeks before service is restored.

The Tonga Cable links up to the Southern Cross Cable, which is part-owned by Spark and which remains fully operational. 

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TVNZ's Pacific reporter Barbara Dreaver's update on the situation.

Back in New Zealand, where we have our own share of active volcanoes, fibre optics are set to be used to detect small earthquakes that could indicate volcanic activity under Auckland's volcanic field.

The area comprises of 53 volcanoes and there's limited understanding of the likely timing and magnitude of future eruptions. GeoNet's 11 seismometers in the Auckland region pick up seismic activity, but now scientists are zooming in to focus on low magnitude quakes that would give a better understanding of volcanic activity.

A team of Victoria University and University of Auckland researchers will use the fibre optic cables that deliver voice and data services around the Auckland region to detect earthquakes of less than magnitude 1.

It's all in the stretch

Using Distributed Acoustic Sensing (DAS) technology, they'll send laser pulses down unused dark strands of fibre on cable links to measure the extent to which cables stretch in small earthquakes. The team will be able to detect stretching every ten metres along a fibre optic cable, which could be stretched slightly as a seismic wave passes.

This method will give them much finer detail when it comes to the small earthquakes that indicate volcanic activity is brewing beneath Auckland.

"We know there is likely to be an eruption in the AVF sometime in the future and we think that earthquakes might provide some insight into volcanic unrest in the area. Being able to accurately monitor seismic signals is essential to forecast the location and timing of an eruption," says research leader Dr Chamberlain.

His aim is to build a catalogue of earthquakes in the Auckland region that existing sensors haven't been able to detect. The method could be applied to fibre optic networks and undersea cables around the world. 

The researchers are using technology from FiberSense, an Australian company that uses fibre optics to measure vehicle movements and monitor infrastructure underground.

The project kicks off in April and is funded through EQC's Biennial Grants programme, which this year awarded $1 million in funding to 13 researchers for projects looking at natural hazards and their impacts.


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