While we can’t predict when earthquakes will occur, scientific research has shown that the Alpine Fault has an unusually regular history of producing large earthquakes. Over the last 8000 years, the Alpine Fault has ruptured 27 times, on average that’s every 300 years. The last significant quake on the Alpine Fault was in 1717. The next severe earthquake on the Alpine Fault is likely to occur within the lifetime of most of us, or our children.
Research conducted by the University of Canterbury, University of Otago and GNS Science has assessed some of the environmental impacts we can expect from the next earthquake of Magnitude 8 or greater on the Alpine Fault. Until now, however, there has been no comprehensive study of the impacts a rupture would have on people living in communities across the South Island and our infrastructure.
Project AF8 (which stands for “Alpine Fault Magnitude 8) is a three-year programme of scientific modelling, response planning and community engagement designed to address that knowledge gap. It’s a partnership of all the Emergency Management Groups in the South Island, funded by the Government through the Ministry of Civil Defence & Emergency Management’s Resilience Fund. It involves scientists from six universities and Crown Research Institutes, emergency services, lifelines, iwi, health authorities and many other partner agencies. The project is managed by Emergency Management Southland.
You can read more about the Alpine Fault here: https://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Major-Faults-in-New-Zealand/Alpine-Fault
Project AF8 – Frequently Asked Questions
Q: What does “AF8” stand for?
A: It stands for Alpine Fault magnitude 8 earthquake. Geological studies have shown that an earthquake of this magnitude occurs on the Alpine Fault at regular intervals. Project AF8 has been set up to assess the impacts that the next such earthquake will have on South Island communities and infrastructure, help people understand and prepare for this inevitability, and develop a planning framework for a coordinated response.
Q: Sometimes you talk about an earthquake and sometimes a rupture. What’s the difference?
A: Basically they are the same thing – a fault ruptures during an earthquake. When an earthquake happens the ground moves on one side of the fault relative to the other. One of the physical outcomes of an earthquake can be surface rupture. This is where the earthquake breaks the ground surface, and is a visible sign of the movement that has occurred along the fault, where the built environment can be significantly damaged because of movement across the fault.
Q: Would a magnitude 8 earthquake on the Alpine Fault cause a tsunami?
A: It’s possible that an earthquake on the Alpine Fault could generate a local tsunami. The Alpine Fault is more than 600km in its full extent, and extends from offshore in Fiordland, right up to southern Marlborough. The scenario that the Project AF8 scientists believe is the most probable focusses on a rupture of the fault from Milford Sound to Lake Kaniere. In this scenario, the southern parts of the fault could rupture across the seafloor and, depending on movement across the fault during the earthquake, could generate local tsunami. Shaking from such an earthquake will cause rockfalls and landslides. Where these occur into lakes, fiords, or other waterways, or offshore under the sea, they have the potential to generate significant tsunami waves and present a threat to people and the built environment around waterways and the coast.
Q: What impact would a big earthquake on the Alpine Fault have on other faults in the South Island?
A: Earthquakes release seismic energy, and it is well understood that some of this energy can be redistributed onto other faults, which is often where aftershocks happen. We cannot discount that an Alpine Fault earthquake could trigger other seismic activity, in the same way as has occurred after the Canterbury earthquakes of 2010-2011 and the Kaikoura earthquake of 2016. However, the nature and extent of seismic loading onto other structures is very difficult to measure and impossible to predict with any degree of certainty.
Q: Will a major earthquake on the Alpine Fault only affect the South Island?
A: No. Just as the Kaikōura earthquake in 2016 had a significant impact on Wellington, we expect that when the Alpine Fault ruptures in a large magnitude earthquake it will be widely felt across the lower North Island. Project AF8 is focused on planning for this event in the South Island, but some North Island CDEM groups are also taking the Alpine Fault into account in their planning. We hosted a national agencies AF8 workshop in Wellington during the development of the draft SAFER Framework. The Ministry of Civil Defence & Emergency Management is planning to run a national exercise based on the AF8 scenario in 2020.
Q: What’s the difference between the magnitude of an earthquake and its impact?
A: Magnitude relates to the amount of seismic energy that is released by an earthquake. The impact an earthquake has on a region or community will also be influenced by its proximity to the earthquake rupture, and its vulnerability to earthquake-induced hazards, such as ground shaking, landslides, liquefaction, and tsunami, for example. ‘Intensity’ is a commonly used simple metric to refer to the amount of damage an earthquake causes to the built environment. It’s measured using the Modified Mercalli Scale. As an example: A large earthquake which occurs in a remote location, or is deep beneath the earth’s surface may cause less damage to the built environment than a smaller but shallower quake that is located near a built-up area. The two Canterbury earthquakes of September 2010 and February 2011 illustrate this: the 7.1 magnitude earthquake of 4 September was centred near Darfield, about 40km west of Christchurch and about 11km deep. Though it caused widespread damage across Canterbury and one death, its impact was less than the magnitude 6.3 earthquake which occurred on 22 February 2011, centred 10km south east of the city centre, 5km deep.
Q: Is it likely that the Australian and Pacific Plates might stop pushing against each other and start moving away from each other, releasing the pressure?
A: It is not likely to do so anytime soon! The plate boundary that is located across New Zealand has existed for more than 20 million years. The relative motion between the Australian and Pacific plates today involves the Pacific plate moving south-west past the Australian plate, with some compression across the Southern Alps and this situation has been happening for around the last 5 million years. These massive tectonic forces change and evolve through geological time, and it is highly likely that in future these forces will continue to change. However, human timescales are much shorter, so we are not likely to see any significant change within the lifetimes of New Zealanders.
Project AF8 timeline
2016-17 Scientific modelling to develop the most credible scenario for a rupture on the Alpine Fault.
This work began in August 2016. Thirty specialists from New Zealand Universities, Crown Research Institutes and consultancies came together as a multi-disciplinary team under the leadership of Dr Caroline Orchiston. They reviewed what was already known about the Alpine Fault and developed a scenario for the next severe earthquake and the foreseeable impacts, which then formed the basis of planning for a coordinated response in the week immediately following the next rupture.
The science workshops were followed by a series of forums across the South Island and in Wellington. These introduced the Alpine Fault earthquake scenario to each Civil Defence Emergency Management (CDEM) Group and our partner agencies and kickstarted local discussions about the practicalities and challenges of responding to a significant earthquake. Click here to read the reports from each workshop.
2017-18 Development of the “SAFER Framework” – the South Island Alpine Fault Earthquake Response Framework
The South Island Alpine Fault Earthquake Response (SAFER) Framework applies the scientific modelling to a coordinated response across the South Island to a significant earthquake on the Alpine Fault. The framework covers the first seven days after the quake. It assumes that in the initial stages of response, each region will react independently according to its immediate needs but in a coordinated manner enabled by the common approach and priorities established through the SAFER Framework.
The Draft Framework is currently being reviewed and will be adopted by 30 June 2018. Once adopted, it will be available on this website and widely shared.
2018-19 Engagement, Planning and Preparing
Once the SAFER Framework has been adopted, each CDEM Group and agency will use it to focus on detailed preparation and planning. That means engaging our communities, iwi, lifelines agencies, emergency services, businesses and a host of others to plan and prepare in a coordinated way for a severe earthquake on the Alpine Fault. The result will be a coordinated, mutually supportive, sustainable response across the South Island, to minimise loss of life and provide for the immediate and short-term needs of our affected communities.
2019-20 Transition to Programme AF8.
Fully preparing for a significant earthquake on the Alpine Fault will continue long after the three years of national funding for Project AF8. The intention is that the Project will transition to an ongoing programme of planning, preparedness and activity. MCDEM has scheduled a national exercise in 2020 based on an Alpine Fault rupture.