Laser Technology On Subsea Cables Could Provide Earlier Tsunami Warning For The Pacific

Ultra-stable laser technology is being used to detect earthquakes in the Southwest Pacific thanks to an inventive method known as optical interferometry on seafloor cables.

GNS Science’s Rapid Characterisation and Tsunami programme (RCET) will collaborate with the UK’s National Physical Laboratory (NPL) and the Measurement Standards Laboratory of New Zealand (MSL) to trial the pioneering detection technique on a non-traffic carrying fibre section of the approximately 4,000 km-long Southern Cross NEXT cable that connects New Zealand to Australia.

In the seismic detection technique developed by NPL, a laser sends ultra-stable light along the seafloor cable, which is then returned by each of the telecommunications amplifiers spaced roughly 50 to 70 km apart along the cable. These returned signals are analysed for differences from the expected norm, and these variations are further investigated to identify potential earthquake or tsunami signatures.

Funded by New Zealand’s Quantum Technologies Aotearoa programme, MSL will upgrade the laser it installed last year to a new high-accuracy laser at one end of the non-traffic carrying fibre optic telecommunications cable that can measure changes in strain within the fibre caused by undersea disturbances such as earthquakes and, hopefully, water displacement from tsunamis.

The method has already shown promising results in the Pacific with signals from the 7.2 magnitude Vanuatu earthquake on 17 December clearly showing up on the sensors. During this trial, it is expected the signal from the new lasers will produce a clearer and more accurate reading that can be used to inform a tsunami assessment.

GNS seismo-tectonophysicist, RCET programme lead and member of the UNESCO Intergovernmental Coordination Group for the Pacific Tsunami Warning System, Dr Bill Fry, states using a non-traffic carrying fibre on the Southern Cross NEXT cable in these pioneering tests will show the potential of this technology towards greatly increasing the density of New Zealand’s tsunami sensor network.

“This approach is effectively tantamount to having around 70 additional tsunami sensors lined up like infantry on the seafloor across the Southwest Pacific to alert us to a tsunami threat the instant a significant change in the ocean is detected,” Dr Fry said.

MSL Senior Research Scientist Dr Johan Grand said the South Pacific is an ideal natural testbed due to its high seismic activity.

“By harnessing cutting-edge optical fibre technology, this collaboration demonstrates how existing undersea infrastructure can address the vast data gap in ocean monitoring, offering transformative possibilities for earthquake detection and ocean current analysis,” Dr Grand said.

“This technology has the potential to revolutionise early warning systems for earthquakes and tsunamis, offering a cost-effective, reliable solution that could save lives and reduce coastal damage.”

Dr Fry said that from the data collected, scientists should be able to infer whether a tsunami has likely been generated, the direction it is travelling and its distance from New Zealand and Pacific neighbours.

“Team that with ‘gold-standard’ DART data, such as wave height, and data inversion techniques developed under the RCET programme, and we can build a pretty accurate picture of how a tsunami will evolve including if and when it will arrive at our shores, how high the waves will be, and how long we need to stay away from our coasts once we know the wave is coming,” Dr Fry said.

This inventive initiative is a significant leap toward meeting the UNESCO-IOC Ocean Decade Tsunami Programme goal of enhancing systems’ capacity using suitable technologies to issue actionable and timely warnings for tsunamis from all identified sources to 100% of coasts at risk by 2031.

“This is an awesome and creative example of using existing data sources and global expertise to increase our eyes and ears in the vast expanse of the Pacific Ocean. We believe that adding these new cabled data to our monitoring network will complement our rich DART data and collectively deliver faster and better warnings that will save lives in Aotearoa and across the Pacific,” Dr Fry said.

National Physical Laboratory Principal Scientist Giuseppe Marra said they are very excited to have started detecting earthquakes and ocean currents in the Tasman Sea.

“This is the very first test of this technology in the Pacific Ocean, and the waters surrounding New Zealand are the ‘perfect laboratory’ to demonstrate the full potential of these innovative cable-based ocean monitoring techniques for Earth sciences and coastal population protection. This very successful UK-NZ project shows how exciting science can bring together countries at the opposite side of the world and we look forward to more collaborative work with New Zealand,” Dr Marra said.

The optical interferometry technique has previously successfully detected earthquakes in the Atlantic Ocean. Measurements in the more seismically active Southwest Pacific will be collected until December 2025 and used to refine the technique, paving the way for integrating other existing infrastructure to increase the world’s tsunami detection network.

“Harnessing the power of multidata is really the next horizon in building our resilience to natural hazards. Each of these advancements opens opportunities for future research to tackle outstanding hazard challenges – such as earthquake early warning and forecasting locally generated, fast-approaching tsunami,” Dr Fry said.

The international collaboration was enabled by the UK’s International Science Partnership Fund and is supported by the New Zealand’s Quantum Technologies Aotearoa programme.

RCET is funded by the MBIE Endeavour Fund. Following significant seismic events, RCET’s tools and expertise deliver enhanced rapid science directly to emergency management and to the public, on the GeoNet website.

GNS Science provides tsunami science advice to the National Emergency Management Agency (NEMA). Only messages issued by NEMA represent an official warning status for New Zealand.

For a local-source tsunami which can arrive in minutes, there is not enough time for an official warning, it is important to recognise the natural warning signs and act quickly. If an earthquake is LONG or STRONG, GET GONE.

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