GNS Science

Alpine Fault is due for a quake that would shake the South Island

Embargoed until: Publicly released:

The lengthy Alpine Fault, which runs along the spine of New Zealand's Southern Alps, has garnered much attention of late as it has a clear geographic record of rupturing every 300 years or so. Last year marked the 300th anniversary since the last such quake – a M8.1 that moved the southern side eight metres further south in a matter of seconds. In a special issue, the New Zealand Journal of Geology and Geophysics has invited local researchers to collate what we know about past quakes on the fault, and how we can prepare for the next big one.

Journal/conference: New Zealand Journal of Geology and Geophysics

Organisation/s: GNS Science, University of Otago, Victoria University of Wellington, University of Canterbury

Media Release

From: GNS Science

Alpine Fault research the subject of special-issue of geology and geophysics journal

Landslides and surface fault ruptures could potentially cause blockages at more than 120 locations on South Island highways after a rupture of the Alpine Fault, according to a study.

Some of the blockages could take more than six months to restore and necessitate the evacuation of large numbers of tourists by sea and air, said the study led by Tom Robinson of from the Geography Department of Durham University in the UK.

The study used the impacts of the magnitude 7.8 Kaikōura earthquake in November 2016 as a guide to the potential effects of an Alpine Fault rupture. It said there should be contingency plans for the evacuation of large numbers of people and the provision of emergency supplies to local populations who could be isolated for extended periods.

The scenario used for the study was a magnitude 7.9 earthquake on the Alpine Fault with 350km of surface rupture between Charles Sound in Fiordland and Hokitika.

“Examining the response to the Kaikōura earthquake is a useful analogue to highlight valuable lessons that can help with planning for the next Alpine Fault earthquake,” said Dr Robinson, who worked at Canterbury University for five years before taking up his present position at Durham University.

The study is one of 12 research papers on the Alpine Fault published this week in a special issue of the New Zealand Journal of Geology and Geophysics. The special volume marks the 300th anniversary of the last rupture of the Alpine Fault in 1717.

The Alpine Fault runs about 500km up the western side of the South Island between Milford Sound and Marlborough. Scientists have studied evidence of its last 27 ruptures over the past 8000 years and calculated that it ruptures at intervals of 291 plus or minus 23 years producing an earthquake of about magnitude 8.1.

GNS Science, which co-ordinated the special issue, originally planned to have it released last year but the Kaikōura earthquake diverted a lot of research effort and its release was postponed until now. GNS Science staff are lead authors on five of the 12 papers.

The New Zealand Journal of Geology and Geophysics publishes four volumes a year and a special issue every couple of years. Six special issues have been published since 2010.

Chief Guest Editor of the special issue Phaedra Upton, of GNS Science, said the Alpine Fault had a well documented history of producing large earthquakes at fairly regular intervals and there would be another one at some time in the future.

“Whatever we can learn about this fault and how it moves will help us understand and prepare for the next great earthquake,” Dr Upton said.

There had been intensive research on the fault over the past two decades and the special volume provided a sample of the latest thinking across a number of disciplines. It contains papers on tectonics, seismology, paleoseismology, landscape evolution, physical impacts and social science.

“The collection provides an insight into the range of research currently being undertaken, but it is by no means a complete picture.”

One of the papers introduces Project AF8, a collaborative effort to save lives by preparing for a magnitude 8 earthquake on the Alpine Fault.

Lead author, Caroline Orchiston of the Centre for Sustainability and the University of Otago, said the potential impacts of the next rupture on the fault continue to increase as New Zealand’s population grows beyond 4.5 million people.

“Project AF8 represents the first effort to co-ordinate disaster response planning for a major Alpine Fault event in the South Island, as well as other large sources,” Dr Orchiston said.

The project has developed scenarios so South Island communities can plan how they might respond to impacts such as road closures, power losses, fatalities, injuries, and social dislocation.

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