25 May 2023

Fibre cables offer scientists unprecedented proximity to Alpine Fault seismic zone

6:39 pm on 25 May 2023
The Alpine Fault is marked out on satellite images by the western edge of the Southern Alps snowline.

The Alpine Fault is marked out on satellite images by the western edge of the Southern Alps' snowline. Photo: NASA

A new study of Chorus' fibre network aims to help scientists understand the internal structure of the Alpine Fault.

Chorus, New Zealand's largest provider of ultra-fast broadband, Victoria University of Wellington - Te Herenga Waka, and the Australian National University are working together on a first-of-its-kind study of the Alpine Fault.

It is hoped the experiment will enable scientists to better model possible seismological scenarios in the event of a major earthquake.

A major rupture of the Alpine Fault in the coming decades is considered likely, with a 75 percent chance of a magnitude 7.5 or larger earthquake occurring in the next 50 years.

Chorus head of contract management Rob Broadbridge said New Zealanders had a keen interest in earthquakes and enabling this research would help to inform earthquake preparation across the world.

A team of seismologists have attached a laser device known as an interrogator to Chorus' fibre cables buried beneath the ground to the north and south of Haast, on the West Coast.

Approximately three kilometres southeast of Haast, the Chorus fibre cable crosses the Alpine Fault itself, allowing unprecedented proximity of DAS (Distributed Acoustic Sensing) instrumentation to one of the world's most closely-watched zones of seismic activity.

Australian National University professor Meghan Miller said it appeared to be the first DAS experiment directly across a major plate boundary which was an "unprecedented opportunity".

"We can't predict earthquakes, but we can prepare for them. So this is one of the better ways to prepare for them and to understand how faults work."

Victoria University of Wellington - Te Herenga Waka Professor of Geophysics John Townend said right now, we were very late in the typical cycle between one big earthquake and the next.

"We know that the Alpine Fault produces really big earthquakes quite frequently, compared to other large faults elsewhere. It hasn't done so in slightly over 300 years, and in the context of its long-term behaviour that's quite a long period of time."

"We need to understand what sort of earthquakes are possible and how they will unfold. That involves looking at the small earthquakes occurring daily to understand the internal structure of the fault zone and what that might mean for the next big quake."

The study will benefit communities, local and central government, emergency services and other humanitarian agencies and will likely be significant in informing preparedness and disaster management.

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