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'Better than a coin toss' - Research reveals significant Alpine Fault earthquake risk 'higher than previously thought'

The Government says new research in the Alpine Fault, supports their work in planning and preparing for severe earthquakes.

Geologists expect to gain knowledge of earthquakes from core samples of the Alpine Fault. Source: istock.com

New research has revealed the chances of the South Island’s Alpine Fault generating a damaging earthquake in the next 50 years are much higher than previously thought.

A study, led by Te Herenga Waka—Victoria University of Wellington senior lecturer Dr Jamie Howarth, shows the probability of such earthquake occurring before 2068 is about 75 per cent.

“While we can never predict when an earthquake will happen, we have known for some time that the Alpine Fault is capable of generating a severe earthquake and our emergency response and management system has been developed on this basis,” Acting Emergency Management Minister Kris Faafoi said in a statement today. 

“The new science doesn’t change the likely impacts for communities in the region. It does, however, confirm our approach to, and investment in, hazard-specific planning and earthquake awareness education has been the right one.

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Victoria University’s Jamie Howarth says it would likely cause large landslides that mirror the 2016 Kaikōura earthquake. Source: Breakfast

“This latest study follows decades of research into the hazard presented by the Alpine Fault. As a result of this our key agencies (the National Emergency Management Agency, the Earthquake Commission and Civil Defence Emergency Management Groups) have a robust understanding of that risk, with that research being the basis of coordinated preparedness action since 2016,” Faafoi said.

Until now, it had been thought the likelihood of a quake was about 30 per cent, based on sequences of sediment deposited adjacent to the Alpine Fault in northern Fiordland, a statement from the University of Wellington said today.

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That’s according to Victoria University research which shows a 75 per cent chance the Alpine Fault will rupture in the next half century. Source: Breakfast

“Scientists from Victoria University of Wellington, the University of Otago, GNS Science, the University of California, and the United States Geological Survey also calculated there is about an 82 per cent chance the earthquake will be of magnitude 8 or higher,” the statement said.

The study, funded by EQC and the Rutherford Foundation, has now been published in Nature Geoscience.

EQC funds a range of research on natural hazards that helps to better understand New Zealand’s risks.

The Alpine Fault is a more than 850km-long split in the Earth’s crust marking where the Australian and Pacific crustal plates meet and grind against each other, creating the Southern Alps.

Howarth says this earthquake gate may help with forecasting the size of future Alpine Fault earthquakes.

“From the record of past earthquakes, we can determine that the probability of a magnitude 7 or higher event is about 75 per cent in the next 50 years. So we now know the chances of seeing a large Alpine Fault earthquake in our lifetime are better than a coin toss.

“That is a really significant result but we can’t forecast the magnitude of the next event from these data alone,” Howarth said.

“This finding doesn’t change the fact the Alpine Fault has always been hazardous.”

“But now we can say the next earthquake will likely happen in most of our lifetimes. We need to move beyond planning the immediate response to the next event, which has been done well through the AF8 programme, to thinking about how we make decisions about future investment to improve our infrastructure and community preparedness.”

Assistant professor Nicolas Barth from the University of California, Riverside, said the fault appears to be a straight line from space, but the reality was different.

“In reality it has variations in geometry and slip rate and is split up into different segments," Barth said.

“If you just run the model on a fault with no geometric complexity, then you just get through-going earthquakes, so they are just magnitude 8 all the time."

“But when you actually include all the geometric complexity that occurs here, then you get the behaviour we have observed, with phases of passing and terminating ruptures.”

Faafoi said the Government's action plan includes:

  • Project AF8 - a multi-regional collaboration between the six South Island and the Wellington Civil Defence Emergency Management Groups and their partner organisations, supported by NEMA funding - has produced detailed planning for coordination of the first seven days of response following a severe Alpine Fault
  • Increased capability and capacity of NEMA’s National Planning Team to develop a National Response Framework to support regional planning in the case of an AF8 event
  • The establishment of the Emergency Management Assistance Team (EMAT) – a squad of specially trained emergency managers who can go wherever needed at very short notice to assist and support local teams to manage emergencies across all hazards and risks
  • Engagement with communities, lifeline agencies, emergency services, businesses and a host of other organisations to plan and prepare for a severe earthquake on the Alpine Fault
  • AF8 is currently running roadshows to provide South Island communities in areas most likely to be affected by a major earthquake, with direct access to scientists and hazard impact information