How Wellington’s ‘hidden communication web’ is helping us better understand earthquake risks

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The new technology means fiber optic cables effectively serve as “virtual seismic sensors” in areas without traditional seismometers. (File photo)

When a magnitude 5.8 earthquake struck near Wellington last month, about 44,000 people reported feeling the shaking.

But beneath the city’s centre, hidden fiber optic cables were also recording the shaking, providing scientists with information on the impact – right down to individual buildings.

The new technology by FiberSense​, a leading infrastructure sensing and monitoring company, is helping shed light on earthquake risks in more densely populated centres.

Mark Englund, FiberSense’s founder and chief executive, said cross-referencing their measurements taken from the recent quake with that of official earthquake sensors had led to remarkable results.

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“The most compelling finding is that because the fiber-based method constantly records the activity as the event wave moves across the earth, our DigitalSeismic service captured the peak ground acceleration with around 1000x greater fidelity compared to what conventional seismic networks achieved.”

The new technology acts as a series of “virtual seismic sensors” set every few meters along fiber cables, with the sensors able to detect the force and speed of the earthquake as the damaging waves move through city blocks and even buildings.

This information captured in real time and available almost immediately as it is automatically stored in the cloud.

Anna Kaiser​, a senior seismologist at GNS, said it was “rapidly developing technology”.

Compared with traditional seismometers, which measure seismic waves with high accuracy at a specific location, the new technology measured pulses of laser light traveling inside fiber-optic cables.

“During an earthquake this traveling light is altered in a way that is measurable and can say something about the movement of the ground between points along the cable,” she explained.

This meant the data was less precise in that it was “nosier”.

Supplied

Anna Kaiser, Senior Seismologist, GNS Science, says the new technology could help give more information quickly in urban centres.

While it did not replace the need for traditional seismometers, necessary for many scientific and engineering applications, the technology had the potential to improve the quantity of data where there weren’t seismic instruments, Kaiser said.

“One of the ways this technology holds promise, for hazard response, is to provide rapid densely-spaced estimates of ground shaking in urban centers that could supplement the high-precision information from traditional seismic networks,” she said.

Senior geoscientist at GNS Richard Kellett​, said the fiber network could effectively act as a “network of virtual seismometers every 10 to 20 metres”.

This increase in station density may provide better spatial resolution, he said.

ROSS GIBLIN/STUFF

FiberSense engineer Hadleigh Coffey explains how fiber-optic network is being turned into a giant sensor, capable of detecting underground water leaks, earthquakes and overhead traffic.

FiberSense’s vice president of research and development Dr Nate Lindsey​ described the cables as a “hidden web of communication within a city”.

It used this web to take the pulse of a city, “block-by-block, building-by-building” so that when an earthquake struck it could compare measurements taken at positions every few metres along the optical fiber.

This improves on traditional seismometers which are often several kilometers apart and allows scientists to better understand the impacts of seismic activity in densely-populated areas where fiber is commonly located, Lindsey said.

This was a “game-changer” which would help first responders, utility companies, critical infrastructure owners and seismologists, as well as government authorities in assessing the damage from earthquakes.

“Whilst we can’t prevent natural disasters occurring, we can inform the way we plan for and respond to these inevitable events. It is critical that the quality of the data we base our recovery plans on should be as complete and well-informed as possible.”

FiberSense is also working with seismologists at University of Victoria, Wellington and University of Auckland to study its earthquake recording with support from EQC.

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