New scientific research published this week reveals the chances of the South Island’s Alpine Fault generating a damaging earthquake within the next 50 years are much higher than previously thought. 

The research, led by Te Herenga Waka–Victoria University of Wellington senior lecturer Dr Jamie Howarth, shows that the probability of that earthquake occurring in the next 50 years has increased from 30% to about 75% and there is an 82% chance the earthquake will be of magnitude-8 or higher.  

 Until now, it had been thought to be about 30 per cent, based on sequences of sediment deposited adjacent to the Alpine Fault in northern Fiordland.

Scientists from Victoria University, 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.

“While we can’t predict when an earthquake will happen, this is a timely reminder of the importance of preparing for an emergency and the steps we can take to keep ourselves, our whānau and our communities safe,” Howarth says. 

One of the researchers’ findings is that a curious “earthquake gate” on the fault south of Jackson Bay, near Martyr River, appears to determine how large an Alpine Fault earthquake gets.

 The Alpine Fault is 850km long, and how much of that breaks in any given earthquake determines the magnitude and impact.

It extends from offshore at the bottom of Fiordland all the way to Cook Strait. It goes onto the land at Milford Sound, travels up the base of the Southern Alps, then does a dogleg through northern Marlborough to go offshore at Cloudy Bay.

Until this work, most of the information on the pattern of past earthquake behaviour was from a single site near Milford Sound.

The new research provided long earthquake records from multiple sites along about 350km of the fault, from Milford Sound to around the Hokitika area – the part of the fault that produces the largest earthquakes most often, compared to anywhere else on the fault.

The best forecast was there was an 82% probability the next such earthquake will pass through the gate and cause an earthquake of magnitude-8 or higher.

Useful tips to help you get ready: 

• Practice ‘Drop, Cover and Hold’ regularly - it stops you being knocked over, makes you a smaller target for falling and flying objects and protects your head, neck and vital organs.
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• Make a plan to get home, work and community ready so that wherever you might be, you’re prepared and talk about it with your loved ones so that everyone knows what to do: https://www.otagocdem.govt.nz/. 
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• Create or update your emergency kit today with supplies to last you 7+ days.  You can either make your own or buy a kit and add your own items to it: https://www.otagocdem.govt.nz/get-home-ready.
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• Make your home safer by ensuring objects that could fall and hurt people are either relocated or fixed/fastened to the wall or floor. Visit https://www.eqc.govt.nz/be-prepared for more information. 
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• Sign up to Otago Gets Ready for text/email alerts (this is one of Civil Defence’s tools to provide advice for emergency situations that affect you personally including floods, fires etc.).  It also gives you the opportunity to list any skills, resources or vulnerabilities which helps Civil Defence to plan and get help more quickly to where it’s needed most.
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• For more information on earthquakes and how to prepare, visit https://www.otagocdem.govt.nz/hazards/earthquakes  

How we’re getting ready: 

The New Zealand government, Emergency Management Otago and the other five South Island Civil Defence Emergency Management (CDEM) Groups, and the science community have been working to improve our capability as a nation to respond and recover from a future Alpine Fault earthquake.  

AF8 (Alpine Fault magnitude 8) is an award-winning programme of scientific modelling, response planning and community engagement, which continues to work to build collective resilience and preparedness to the next major South Island earthquake event. 

For more information visit https://af8.org.nz/.