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Following the 1968 Inangahua earthquake, the road through Buller Gorge and all roads in and out of Inangahua were blocked by landslides, and over 100 km of railway track was damaged

Alpine Fault reality drives unified quake response – By Iain MacIntyre

New appreciation that a magnitude 8 earthquake recurs at roughly a 300-year frequency on the Alpine Fault – where the last rupture occurred in 1717 – has stimulated the rapid development of a collective South Island plan of response and resilience.

Initiated in the middle of 2016, the Ministry of Civil Defence & Emergency Management (CDEM)-funded and Emergency Management Southland-led Project AF8 (‘Alpine Fault Magnitude 8’) was prompted by a significant discovery of alternating soils and silts at Hokuri Creek in Southland.

In a sobering presentation at last October’s NZ Airports conference, University of Otago Centre for Sustainability deputy director/senior research fellow and AF8 science lead Caroline Orchiston confirmed that subsequent modelling has revealed that the next big event is “inevitable”.

“We settled on what was considered the most scientifically-credible option of an epicentre in the south of the fault right off Milford Sound, with the energy travelling mainly out towards the northeast,” says Ms Orchiston. 

The Alpine Fault – over the last thousand years, there have been four major ruptures causing earthquakes of about magnitude 8, with the most recent in 1717 – Image courtesy of Project AF8

An animation of that scenario depicts earthquake waves advancing at about 3 km per second and resonating significantly in the Canterbury basin due to its deep sedimentary base. Within two to three minutes, those waves would reach the Nelson/Marlborough area and would cause damage as far away as the lower North Island.

Ms Orchiston says the AF8 scenario predicts hundreds of fatalities and thousands of injuries – exact numbers being dependent on the time of day and year, as well as basic human behaviour in the event.

The launch of SAFER

Having raised awareness through a series of regional workshops as well as its website and social media, Project AF8 has also workshopped the scenario with the six South Island CDEM groups and partner organisations. With foreseeable impacts on communities and confirmed collective capabilities duly identified, a coordinated response was launched last October.

Known as the South Island Alpine Fault Earthquake Response (SAFER) plan, this framework is described as providing a concept of coordination of response and priority setting across the CDEM groups and partner organisations in the first seven days following a major earthquake.

Although acknowledging the stimulus for initiating the project and developing the framework was the specific AF8 scenario, CDEM Southland group controller Angus McKay clarifies the work has much wider application. “We’ve designed the SAFER framework so it can be used during any major earthquake in the South Island, not just an AF8,” he says.

“The main issues are about coordination and prioritisation of effort during a major event, so that doesn’t really change if it is an AF8 or a Marlborough Fault system earthquake – for example, the Hope Fault. 

“The work done in AF8 has also improved our ability to respond to any event, building strong networks between science and emergency management, and working with iwi and communities to discuss preparedness.”

Critical lifelines

Although noting that South Island airports/aerodromes offer a ‘critical lifeline’ in an emergency response, Ms Orchiston says the AF8 scenario predicts widespread damage to such facilities, with some likely to be rendered non-operational.

University of Otago Centre for Sustainability deputy director/senior research fellow and AF8 science lead Caroline Orchiston speaking at the NZ Airports conference

Even for those that remain in action – with Christchurch, Timaru, Oamaru and Invercargill facilities predicted to fare best – their response involvement would be impacted by the highway network being taken out of operation.

On a more positive note, CDEM Otago group controller Chris Hawker says a recent Geosolve geotechnical assessment of Queenstown and Wanaka airports has confirmed that damage to their runways from a severe Alpine Fault earthquake is expected to be ‘negligible to minor’. “Neither airport runway is subject to liquefaction due to the height of both above the groundwater table,” he says.

“This report is significant for planning as it provides a reasonable degree of certainty that should Queenstown or Wanaka become isolated by road, the airports are likely to remain operable. CDEM Otago staff have commenced discussions with Queenstown Airport Corporation about the challenges we might collectively face post AF8 and how we might manage these. This will be an ongoing process over a long period of time and will involve multiple agencies.”

Mr Hawker adds that Dunedin Airport has offered itself as a venue for managing air operations in a large-scale event, and other airports are being assessed as options for other response activities. “An example is Alexandra Airport which could potentially become a refuel location if we were unable to get truck access to Queenstown or Wanaka. In all instances, we have had excellent cooperation from key staff from the airport companies.”

Re-establishing supply chains

Observing that major food suppliers are building new distribution centres around the country, Mr McKay says there is also keen awareness of the role they will have to play in the advent of a natural disaster.

Mr Hawker adds that work continues both to establish greater understanding of the challenges of maintaining the supply of fast-moving consumer goods, and to develop solutions should the supply chain be severed. 

Predicted impact of a magnitude 8 earthquake centred at Milford Sound on the South Island state highway network – Image courtesy of Project AF8

“Fuel and food are the two most critical elements, but there are numerous other ‘must haves’ which would need to be included – an example being during the Kaikoura earthquake response where hand sanitiser became a major issue to help prevent illness among the community. There is a lot of work to be done in this area as we have really only just started down this road.”

A detailed assessment of the Kaikoura earthquake has helped inform AF8 response planning. However, that earthquake had a significantly smaller rupture of 180 km, compared to the 400 km AF8 scenario, notes Ms Orchiston. 

She says that ‘scenario earthquakes’ tend not to transpire as expected, with factors including:

  • • Damage to highways – dispersed social impacts, implications for recovery and isolated communities
  • • Damage across urban and rural settings – prioritisation of response activities (including animal welfare in farming communities)
  • • Cascading events – adverse weather, landslide dams and aftershocks
  • • Tourists – evacuations, media focus and implications for tourism recovery.
She adds: “Recovery takes years and is unique to the places affected.”

The effects on people

On the theme of learnings from the Kaikoura earthquake, Mr Hawker says from personal experience, one of the key issues to address is the effect on people – including first responders.

“Police, firefighters and ambulance staff are all people first, and first responders second, so working with these key agencies – who we look to immediately when something occurs – to help them prepare their staff has been a significant focus of our work,” he says.

“Looking wider, promoting the development of individual preparedness both domestically and commercially is critical to developing resilience, and business continuity plans for all sizes of businesses will be a major benefit on ‘the day’.”

As an aside, Ms Orchiston says the research she undertook on tourism recovery after the Canterbury earthquakes revealed some interesting findings. “There was quite a high awareness of earthquake risks, particularly around the Southern Alps region, but a poor understanding of the consequences and long-term implications. I think there is still a lack of awareness about how long it will take the tourism industry to recover – in Canterbury, it took more than six years for international guest-night figures to rebound to pre-earthquake levels.”

Iain MacIntyre is an award-winning journalist who specialises in transport issues within New Zealand; he can be contacted at i.macintyre@xtra.co.nz

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