This fault has ruptured four times in the past years, each time producing an earthquake of about magnitude 8. Recent research published in by GNS Science has extended our knowledge of the Alpine fault earthquake record back through the past years.
Click here for more details of these findings. Horizontal movement of the Alpine Fault is about 30m per years — very fast by global standards. Each time it has ruptured, it has also moved vertically, lifting the Southern Alps in the process. In the last 12 million years the Southern Alps have been uplifted by an amazing 20 kilometres, and it is only the fast pace of erosion that has kept their highest point below metres.
The glaciers and rivers have removed the rest of the material and spread it out across the lowland plains or onto the sea floor. The rapid uplift also means that faulted rock from deep down has been brought to the surface, and can be studied by scientists. The rupture will produce one of the biggest earthquakes since European settlement of New Zealand, and it will have a major impact on the lives of many people.
Current research includes:. Holes were drilled for explosives, and when the explosives were set off, a multi-channel seismograph recorded the seismic waves. The way the waves are reflected and transmitted tells much about the rocks and structures near the fault.
This method can even indicate rocks rich in high- pressure water, the source of hot springs like those at Hanmer Springs. See this Interactive map of the Alpine Fault and links to a virtual field trip on the University of Otago Geology website. This news article from Stuff covers some research on the frequency of past earthquakes along the Alpine fault. What are the challenges of putting a borehole into a fault?
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Find out more. Plans, Policies, Reports. News and Events. Public Transport. Timetables, fares, FAQs and all the information you need to get around Dunedin. The Alpine Fault connects two "subduction" margins where the ocean floor descends into the Earth's mantle.
At this point the surfaces of the two plates making up the South Islands alpine fault meet. The Pacific Plate on the easterly area of New Zealand is moving westwards and the Australian Plate, on the western side of New Zealand moves eastwards.
They move at a relative rate of about 45mm per year. As these two plates move against each other enormous pressure builds up which must eventually be released through earth movement. The result is a major earthquake along the Alpine fault. The pressure has been continually building for about years since it was last released by a large earthquake in AD. This earthquake is a normal part of New Zealand's evolution.
We are a young country and learning to adapt to it is a necessity if you and your community are to get through. The Alpine Fault earthquake will be but one event of many different types of natural hazard events that will occur in New Zealand's future. The map below indicates the range of the earthquake and its shaking intensity shown in Roman numerals.
The historical patterns of earthquakes and current research on the Alpine Fault indicate that it is likely to rupture very soon in geological terms. Analysis of sediments deposited by previous Alpine Fault earthquakes shows that the faultline ruptures on a remarkably regular basis, on average at intervals around years.
Carbon dating confirms that the last severe earthquake on the Alpine Fault was in You will find more information about the Alpine Fault, evidence of past earthquakes, and what preparations are being made for a coordinated response across the South Island on the Project AF8 website.
This earthquake will occur with no recognisable warning. The rupture of another faultline nearby may trigger it, but we will only know this afterwards. The alpine fault earthquake will alter tectonic stress distribution, and other faultlines may rupture in the days or years following it. The length of the rupture will be up to km, eg.
The earthquake will last for about two minutes. The alpine fault may rupture along part of its length, with lower magnitude, and be followed shortly by rupture of the rest.
Two very large earthquakes or a series of large earthquakes are also realistic scenarios. In some places the force will result in a horizontal earth shift of up to 8 metres, and a vertical displacement of 4 metres.
The effects will be worst in West Otago, diminishing eastward. Significant building damage can be expected in the Queenstown Lakes District. Damage in other parts of Otago will be irregularly distributed depending on the land forms and the built environment. If you would like to know more, there are a series of short presentations by scientists who have been researching the Alpine Fault and the impacts of the next rupture.
The effects will be amplified in South Island mountainous regions and high country where enormous damage can occur to peaks and ridges. Countless landslides can be expected of all sizes.
In areas where the magnitude is plus or minus 9, many tens of millions of cubic metres of rock and scree may collapse from slopes. Damaging aftershocks are likely to continue for several weeks afterwards and the event will have disastrous consequences across many regions. Less intense shaking from aftershocks will continue for months.
There will be liquefaction and widespread ground damage.
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