UK and NZ scientists turn Southern Cross NEXT cable across the Tasman into an earthquake detector

A collaboration between the Measurement Standards Laboratory of New Zealand (MSL) and Britain's National Physical Laboratory (NPL) will create a undersea cable earthquake detection system using the Southern Cross NEXT fibre-optic cable.

Using a technique pioneered by NPL in 2021, derived from ones used in quantum science, the scientists behind the project will test the method on a section of the NEXT cable, which spans 3876 kilometres between New Zealand and Australia across a seismically active area.

The scientists will turn the section of the cable on the seafloor into an array of sensors that can gather environmental data through existing optical fibre infrastructure, with no new hardware required to be installed. 

Data collected from the cable sensor array on the seabed can be used to detect earthquakes and act as a early tsunami warning, the NPL said.

"It is another beautiful example of improvement in measurement giving us access to depths of information that in turn push the limits of our metrology. Not only that, but ​we see precision measurement underpinning our aspirations for a sustainable future.

"Our earliest timekeeping devices - calendars - allowed us to live according to the rhythms of our natural world. And now the next generation of clocks is unlocking a new richness of insight into our planet," Annette Koo, director and chief metrologist, MSL.

Giuseppe Mara, the principal scientist at NPL, explained that the joint UK-NZ project will test the UK laboratory's pioneering seafloor cable-based environmental detection in of the most seismically active regions in the world.

"This will significantly advance research on these innovative environmental sensing techniques, with impact on a number of science areas, from seismology to oceanography, as well as future societal applications, such as in early tsunami warning systems," Mara said.

"This project is a testament to how science is capable of bringing together minds from the world’s antipodes to advance our knowledge of how our planet works and bring positive impact to society," he added.

NPL has already demonstrated the technique in the Atlantic, on a 5860 kilometre fibre-optical cable between the UK and Canada.

Currently, there are only a handful of permanent ocean floor sensors in place around the world, as installing and maintaining them is challenging and prohibitively expensive, NPL said.

The NPL-MSL project is part of a new collaboration agreement with New Zealand, announced by UK Minister for Science, Research and Innovation Andrew Griffith, at the Organisation for Economic Cooperation and Development (OECD) Committee for Science and Technological Policy Ministerial event in Paris.

Using optical fibre cables for sensing purposes is already taking place in New Zealand.

Scientists from Victoria University and The Australian National University have placed sensors on Chorus' fibre-optical cable that crosses the Alpine Fault near Haast, for seismological research.

The scientists are using Distributed Acoustic Sensing (DAS) technology to detect ground motion at the fault, which has a 75% chance of erupting in the next 50 years, possibly causing an earthquake larger than magnitude 8.

By emitting pulses of light, some of which is scattered as it travels along the fibre-optic cable, scientists are able to detect vibrations caused by passing seismic waves. The system generates large amounts of data, around 1 terabyte a day, providing very detailed information of and insights for the Alpine Fault.