What is the Alpine Fault (AF8)?
The Alpine Fault is one of the South Island’s major seismic hazards. The 850km Faultline runs along the mountainous spine of the South Island, marking the boundary where both the Pacific and Australian tectonic plates meet, forcing the Southern Alps upwards.
The last major earthquake on the Alpine Fault was in 1717. It shunted land horizontally by eight metres and uplifted the Southern Alps a couple of metres. Over the past 8000 years the Alpine Fault has ruptured 27 times, on average every 300 years with the last significant rupture occurring in 1717, so I’m sure we can all do the maths on that realising it is well overdue and whilst we cannot predict exactly when the next one will occur, scientific research does show us that the Alpine Fault has an unusually regular history of producing large earthquakes.
An earthquake on the Alpine Fault is likely to be one of the most significant disasters that could affect the Selwyn District (and beyond), causing prolonged water, power, and mobile connectivity outages. It has the potential to produce a magnitude 8+ earthquake with excessive ground shaking (for around three minutes) and other seismic related hazards (e.g., landslides - which could potentially cause lake tsunamis and liquefaction). It will undoubtedly cause major disruption with some longer-term impacts throughout many parts of southern and central New Zealand. All roading networks to the West Coast will be cut off for a prolonged period of time.
To increase our awareness and community resilience to the hazards in our ‘back yard’ so to speak, it is imperative we understand and prepare for an imminent Alpine Fault rupture within the next 50 years.
With the predicted probability (updated as of late 2021) of a 75% chance of a magnitude 8+ earthquake within the next 50yrs we must ‘get ready’. Registering your details on this website is a good first step and you will then receive emergency alerts: https://selwyn.getsready.net.
Selwyn District Council's emergency management team has been working with Selwyn Communities to get ready for some time now developing a district wide Alpine Fault response plan, and has worked with communities to develop plans for the high country. However, there is still insurmountable work that needs to occur to ensure all threads within our communities are linked together for such events.
It is time for each of us to take responsibility to think about how we prepare and make decisions around improving resilience through future investment into infrastructure and community preparedness.
For Businesses it is imperative they enhance their resilience through having robust business continuity plans (that have been tested) to incorporate such predicted disruptions, for example relocation of premises, operating without power (considering backup generators if you are an essential service), water and communication services.
It would be very easy for many of us to just ignore the threat we have in our ‘back yard’ but I cannot reinforce enough how important it is as a community for us to come together and improve our understanding and awareness of the Alpine Fault so we can enhance our community resilience by being better prepared for such events. Building resilience is important for individuals, families and our communities – being resilient and ready helps to minimise stress when the event happens.
How can you prepare?
Develop a plan with your neighbours, friends, families. Consider things like:
- the everyday items you may need - food, water (+- 9L per person for several days), power and medicines;
- always keep some cash on hand - supermarkets will not have eftpos facilities;
- plan how to communicate and work out what you would do if you could not contact your family;
- work out supplies you will need – as a neighbourhood there may be items such as generators and alternate cooking arrangements that you could share.
I encourage you to attend one of the AF8 roadshows that travel periodically around the South Island. To keep up to date view the website: https://af8.org.nz