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Drilling deep into the Alpine Fault


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Kiwithrottlejockey
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« on: July 28, 2010, 11:56:26 pm »


Scientists plan to drill deep into Alpine Fault

By PAUL GORMAN - The Press | 5:00AM - Tuesday, 27 July 2010

Gaunt Creek

TOP INTERNATIONAL SCIENTISTS are eyeing up a scrubby West Coast stream bed to carry out multimillion-dollar research into New Zealand's major "earthquake machine".

The literally ground-breaking work, which could run over several summers, will involve drilling into the South Island's Alpine Fault to understand how large faults evolve and generate earthquakes.

The Deep Fault Drilling Project has applied for resource consent to drill two boreholes about 150 metres deep and 50m apart in Gaunt Creek, near Whataroa, next year.

The location atop the Alpine Fault is said by scientists to be one of only a few such sites in the world.

GNS Science said the project would be one of New Zealand's largest field-based experiments and was an example of "big science".

It will involve 100 or more scientists and require funding from New Zealand, Germany, Britain, the United States, Canada and Australia.

"Scientists have dreamed about doing this for decades," GNS spokesman John Callan said.

"The Alpine Fault is late in its earthquake cycle, so it is seen as a great opportunity to investigate one of the top faults in New Zealand by putting a range of probes down into the zone where earthquakes occur."

"It has been their goal, almost a holy grail of earth sciences."

Project co-leader Dr John Townend, of Victoria University, said the investigation would take place in "an amazing natural laboratory".

The Alpine Fault extends more than 650 kilometres from Marlborough, along the western edge of the Southern Alps to Milford Sound.

Research suggests it ruptures every 200 to 400 years, producing damaging magnitude eight or more earthquakes.

The two boreholes will enable scientists to examine unweathered rocks, install earthquake recorders and weather gauges, and measure temperature and water pressure.

Samples will be analysed using photographs of the interior of each borehole and an X-ray scanner to examine each rock's mineralogy and structure.

Surface surveys will also be conducted using seismic imaging equipment and geological and geochemical mapping.

"The Alpine Fault offers great opportunities to investigate pressure, temperature and chemical conditions in the heart of the ‘earthquake machine’," Townend said.

"The Alpine Fault's geometry, rapid rate of slip, and well-studied surface exposures make it a site of real global importance for fundamental research into the evolution of large faults and the conditions under which earthquakes occur."

"Funding applications ... have been submitted in Germany, the UK, US, Canada, and Australia, as well as New Zealand, and we await the outcomes of these and future applications."

Researchers at GNS Science, Otago University and Victoria University are co-ordinating the work in collaboration with colleagues at Canterbury University and Auckland University, and organisations in Germany, Britain and the United States.


http://www.stuff.co.nz/the-press/news/south-island/3959638/Scientists-plan-to-drill-deep-into-Alpine-Fault
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« Reply #1 on: January 17, 2011, 08:18:16 am »


just keeping up with the play, check here when the drilling starts.   Roll Eyes

http://quake.crowe.co.nz/
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« Reply #2 on: January 25, 2011, 07:20:20 pm »


Faultline drillers on quake project

NZPA | 5:30AM - Monday, January 24, 2011

Scientists hope the study will give them more insight into what happens in the lead up to a quake, such as the one in Canterbury last year. — Photo: Mark Mitchell.
Scientists hope the study will give them more insight into what happens in the lead up
to a quake, such as the one in Canterbury last year. — Photo: Mark Mitchell.


SCIENTISTS will today begin an ambitious project to drill boreholes into the South Island's Alpine Fault, hoping to find out more about how an active fault reacts before and during an earthquake.

The group of international and New Zealand scientists will drill directly into the massive faultline to investigate its structure, mechanics and evolution.

"We don't know what we'll find when we drill into the Alpine Fault. If we knew all the answers, we probably wouldn't be doing this," said project leader Rupert Sutherland of GNS Science.

The boreholes will be about 130m to 180m deep and up to 60m apart at Gaunt Creek near Whataroa, north of Franz Josef on the West Coast. It was the first time scientists had investigated a major active fault in New Zealand by drilling boreholes, he said.

The team planned to install sensors within one of the boreholes to create an underground "observatory" by mid-February.

"This summer is the first step in an exciting long-term project where a New Zealand-led international consortium will drill to progressively greater depths into the Alpine Fault to better understand how large faults work," he said.

Next summer, the group planned to drill about 1.5km into the fault.

Scientists hoped the project would help them understand more about the physical and chemical processes that took place at a fault before and during an earthquake.

"There is considerable international interest in our project at Gaunt Creek as it has the potential to answer a number of important questions about plate boundary earthquakes and the evolution of large faults."

Scientists have previously talked about the potential to drill a borehole up to 5km deep, which could give new clues about what happens in the lead-up to a major quake 10 times as powerful as Canterbury's 7.1-magnitude quake on September 4 last year.

The Alpine Fault, running the length of the South Island, has not produced a large earthquake in three centuries but is regarded as one of New Zealand's most hazardous faults.

The Government has been told that there is a 20 per cent chance of a big quake on the fault in the next 20 years, compared with a 15 per cent chance of a major one affecting Wellington over the next 50 years.

The Alpine Fault runs for more than 650km, from south of Fiordland and along the spine of the South Island into Marlborough. It has moved an average of 27mm a year over the past 50,000 years — but this has included catastrophic quakes in which it has moved 8m in seconds.

It ruptures every 200 to 400 years — producing earthquakes of about magnitude 8 — most recently in 1717 along nearly 400km at the fault's southern end.

A similar project at Parkfield on California's San Andreas Fault cost $44 million and has equipment inserted 3km deep.


http://www.nzherald.co.nz/the-changing-world/news/article.cfm?c_id=1502962&objectid=10701585



An news story from earlier this month....

Scientists set to probe Alpine Fault

NZPA | 7:49PM - Wednesday, January 05, 2011

SCIENTISTS are preparing to drill deep boreholes into the South Island's Alpine Fault, in a bid to uncover clues about what happens before major earthquakes up to 10 times the size of the Canterbury quake.

Though the Alpine Fault, running the length of the South Island, has not produced a large earthquake in three centuries, it is regarded as one of New Zealand's most hazardous faults.

The Government has been told that there is a 20 per cent chance of a big quake on the fault in the next 20 years, compared with a 15 per cent chance of a major one affecting Wellington over the next 50 years.

The Alpine Fault last ruptured 290 years ago and moved the ground 27m horizontally along 300km.

Geophysicist Rupert Sutherland, of GNS Science, is part of a group of 65 international researchers which wants to drill boreholes directly into the faultline — eventually to a depth of 1.5km — to investigate its structure, mechanics and evolution.

Dr Sutherland was last year granted $920,000 over three years to discover what physical conditions in the Earth's mid-crust allow active continental faults to evolve and generate earthquakes, while Jennifer Eccles, of Auckland University, was awarded $300,000 to analyse data from seismometers to be installed at various depths in one of the boreholes.

Millions more dollars are expected to be contributed to the project by overseas researcher so that measurements, analysis of core samples and establishing long-term observatories within the boreholes can provide a basis for future deeper drilling experiments.

The project will be kicked off with two boreholes only 150m deep, but geologists have previously talked about the potential to eventually drill a borehole up to 5km deep, which could give new clues about what happens in the lead-up to a major quake about 10 times as powerful as the Canterbury's 7.1-magnitude quake on September 04 last year.

Preparations for drilling are expected to start on January 24 at Gaunt Creek, near Whataroa, on the West Coast.

Professor Kevin Furlong, from Pennsylvania State University in the United States, told NZPA that the initial boreholes would be shallow, but the project would provide a focal point for a broad range of research into the faultline.


http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10698027
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« Reply #3 on: January 26, 2011, 06:03:25 am »



http://xtranewscommunity2.smfforfree.com/index.php/topic,8702.msg98412.html#msg98412

what they said, plus:

I want to see the core from the holes.  Bugger earthquakes, and national parks - show us the minerals.
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« Reply #4 on: February 10, 2011, 10:01:26 pm »


Alpine Fault dams water to east, study finds

By PAUL GORMAN - Science Reporter - The Press | 7:26AM - Wednesday, 09 February 2011

IMMENSE FORCES along the South Island's Alpine Fault have created a waterproof seal between two of the world's major crustal plates.

Scientists working on the Alpine Fault drilling project near Whataroa on the West Coast have found that a belt of intensely crushed, powdery clay around the immediate fault is keeping huge quantities of water underneath the Southern Alps — on the Pacific Plate - from escaping on to the Australian Plate on the western side of the fault.

Project co-leader Dr Rupert Sutherland, of GNS Science, said the fault was acting like a "large umbrella or dam".

Drilling down into and across the fault had effectively been like "punching a hole in a dam" and had created a sudden waterfall underground.

The speed of flow of water from one side to the other was equal to that of a 33m-high waterfall, he said.

"Right at the beginning we wondered if the fault itself would be a seal for water flow, which is quite important because the fluid processes on a fault make a difference to friction."

"I was quite surprised though at the magnitude of the pressure difference across the rocks."

"The rock has been absolutely crushed into a very fine powder that doesn't let water go through it because it is so fine- grained."

The discovery was one of the first of the international drilling project. More research was needed on the fluid characteristics of the fault zone to be able to draw definite conclusions, Sutherland said.

The project at Gaunt Creek has attracted more than 20 researchers and engineers from around the world.

The Alpine Fault runs more than 450km from Marlborough down the western edge of the Alps and offshore at the entrance to Milford Sound.

Researchers believe the fault ruptures every 300 or so years and last moved in 1717.

It is expected to generate a magnitude-8 earthquake when it next yields to pressure from the Australian and Pacific plates.

Sutherland said site work would be completed in the next day or two.

The project's underground fault observatory was now in place, with five fluid pressure sensors, 25 temperature sensors and two seismometers installed underground in the two bore holes.

The drilling crew had sealed the bottom 100m of the 151m hole with a cement and bentonite (clay) solution and also the bottom 82m of the 100m bore.

Three tonnes of rock cores — about 100m — had been carefully collected and were being sent to Otago University to be analysed over the next few months, he said.

"It's been a complete success, but twice as hard as I thought it would be."

"There's always issues — technically it is very difficult work; the first time it has ever been done."

Scientists might return to drill deeper into the fault next summer, but that still had to be finalised, Sutherland said.


http://www.stuff.co.nz/the-press/news/canterbury-earthquake/4634396/Alpine-Fault-dams-water-to-east-study-finds
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« Reply #5 on: August 04, 2011, 05:25:00 pm »


Council nervous of signposting Alpine Fault

By CHERYL RILEY - Greymouth Star | Tuesday, 02 August 2011

SOME Westland district councillors took a bit of convincing on Thursday about a proposal to to signpost the Alpine Fault.

Christchurch-based Tuatara Tours operator John Dunbier said that promoting the fault, which slashes right through Westland, was an exciting opportunity to ‘grow’ a unique tourist attraction.

However, Councillor Neil Bradley suggested that drawing attention to the Alpine Fault could work in the reverse and tourists could be turned away. Any sign would need to be complimented with an information panel, he suggested.

Councillor John Birchfield said there were information panels about the fault line at Paringa and at the Whataroa tearooms.

Mr Dunbier said the Great Alpine Highway followed the south bank of the Taramakau River and crossed the plate boundary in a spectacular alpine setting.

“It is here at Rocky Point (near Jacksons) that the boundary between the Pacific and Australian tectonic plates should be signposted.”

He believed the proposal would have positive impacts on tourism, civil defence awareness, education and promotion of the Great Alpine Highway.

“There are very few places in the world where it is easy to access such a distinctive and scenic plate boundary.”

Mayor Maureen Pugh said the proposal was “quite novel”.

The council supported the proposal in principal, she said.

Mr Dunbier will now consult with other parties and approach the New Zealand Land Transport Agency.


http://www.greystar.co.nz/content/council-nervous-signposting-alpine-fault
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« Reply #6 on: November 21, 2011, 11:06:53 pm »


Lidar filters bush to reveal Alpine Fault

By PAUL GORMAN - The Press | 5:00AM - Monday, 21 November 2011

LIDAR VS PODOCARP FOREST

TECHNOLOGY that strips away thick bush has given scientists a better understanding of the nature of the Alpine Fault, one of New Zealand's biggest hazards.

An aerial survey of the Alpine Fault using Lidar (Light Detection and Ranging) — in which pulses of energy are fired down at the ground and bounce back — has revealed subtle features in the landscape formed by fault movement over hundreds and thousands of years.

Dense West Coast podocarp forest and under-storey vegetation make it almost impossible for researchers to find parts of the fault on foot.

The survey, flown and processed by NZ Aerial Mapping this year, covered a 34 kilometre-long and 1.6km-wide, high-uplift section of the fault from Whataroa to Franz Josef. Lidar was also used in the natural hazards research platform-funded project to investigate about a 30km stretch of the western part of the Hope Fault from the upper reaches of the Hurunui River to the upper Hope River, much of it under beech forest.

GNS Science earthquake geologist and project leader Robert Langridge said Lidar had been used effectively in California to study parts of the San Andreas fault system underneath redwood forest.

"Without causing deforestation you are making a map that is removing the vegetation ... through some very complex filtering. What you tend to see is very subtle things you would never see in aerial photos or by crashing through the bush in the South Island to find them."

The results of the collaborative work between GNS Science and young researchers at Canterbury, Otago and Victoria universities had thrown up a few surprises, Langridge said.

Earlier work had suggested the central section of the Alpine Fault had sections split into short, stepped, segments about one-kilometre long because of the way the fault reacted with the Earth's surface.

"With Lidar we were able to confirm that theory, [and] also show some of the traces ... were quite extreme in their strike direction, accommodating lots of strike-slip [movement] and considerable amounts of reverse movement. So it has been able to confirm things that we sort of only dreamed about."

At Gaunt Creek, the Lidar had revealed fault traces oriented north-south.

Excavation of a terrace across the fault there showed it last moved in 1717, confirming the date of the most recent rupture, he said.

"There are few places along the fault where we have such good evidence for the faulting during the most recent event."

The density of the survey points had been lowered for the Hope Fault work because the forest cover was less thick.

A student working on the Hope had discovered the zone of ground deformation was wider than it would be with just a single fault. The Lidar allowed all the secondary faults to be mapped.

If funding was available, it would be wonderful to fly along most of the Alpine Fault's 650km length, he said.

"With Lidar we are realising a primary set of data to build other projects off. By knowing where the fault is and main traces, you can do slip-rate studies, trenching studies to date past quakes, and think about where to site deep-drilling projects."

"It's a new form of mapping technology that is going to lead the way for a decade or so."


http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/6002393/Lidar-filters-bush-to-reveal-Alpine-Fault
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« Reply #7 on: April 14, 2012, 03:27:46 pm »


Threat of quake in Southern Alps wanes

By PAUL GORMAN - The Press | 5:00AM - Tuesday, 03 April 2012

The ALPINE FAULT and HIKURANGI TROUGH.

EARTHQUAKE-WEARY South Islanders finally have some good news — the Alpine Fault could still be 200 years away from generating its next quake of about magnitude 8.0.

Scientists have found that the most active central and southern sections of the 650-kilometre-long fault appear to break on average once every 480 years, not about every 300 years as previous studies suggested.

The date of the last huge quake from the fault has been pinpointed as 1717 (plus or minus two or three years), which had meant another major quake might be not far away.

But with an average return period of about 485 years, that quake might not take place for more than 180 years.

The researchers warn, however, that their calculation is based only on a rupture history of the three most recent events they found evidence for — in 1717, 1230, plus or minus 50 years, and 750, plus or minus 50 years.

The work of the researchers from GNS Science, Otago University's geology department, Western Washington University's geology department and Nevada University's seismological laboratory has been published in the April issue of the Bulletin of the Seismological Society of America.

The Alpine Fault runs from Marlborough down the western edge of the Southern Alps and heads offshore close to the entrance to Milford Sound. It marks the boundary between the Pacific and the Australian crustal plates.

The researchers dug five trenches at three sites up to 12km apart on the southern part of the fault near Haast, the Okuru River and the Turnbull River.

The trenches allowed dating of exposed river terrace deposits displaced by quakes and also revealed wood and bark from tree ferns that could be radiocarbon-dated.

Analysis then revealed that in the Haast area since 688 there had been three "large-to-great earthquakes", causing up to nine metres of horizontal displacement and about 1m of vertical movement.

The maximum amount of movement suggested each of the quakes had caused several hundred kilometres of the Alpine Fault to break.

With an average recurrence period of 485 years, the chances were that the next large or great quake was "not imminent", with only 295 years having passed since the 1717 event, the paper said.

"Therefore, the Alpine Fault in South Westland may not be close to rupture, as is often speculated."


The ALPINE FAULT.

Lead author Kelvin Berryman, of GNS Science, said the study had been "15 years in the making".

"The results provide us with potentially some breathing space, that we're not as close to rupture as is sometimes assumed. It gives us food for thought."

The results of another major study of the fault, further south where it crosses the remote Lake McKerrow, were likely to be published this year, he said.

That investigation had looked at the last 20 events, well recorded in stream sediments by the lakeside.

"That further work will extend the record out much further," Berryman said.

"The bigger story is yet to come out."


http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/6682204/Threat-of-quake-in-Southern-Alps-wanes
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« Reply #8 on: April 14, 2012, 03:27:58 pm »


Alpine quake optimism faulted by geologists

By PAUL GORMAN - The Press | 5:00AM - Friday, 13 April 2012

The ALPINE FAULT.

CANTERBURY UNIVERSITY earthquake researchers believe the latest study on the frequency of major Alpine Fault earthquakes is too optimistic.

Scientists from GNS Science, Otago University's geology department, Western Washington University's geology department and Nevada University's seismological laboratory recently found that the southern section of the 650-kilometre-long fault, near Haast, appears to rupture on average once every 480 years.

Previous investigations had suggested the fault breaks about every 300 years. The last great quake, of about magnitude 8.0, was in 1717, suggesting the next one could be due soon.

Lead author Kelvin Berryman, of GNS Science, said the 15-year study — published in this month's Bulletin of the Seismological Society of America — had provided "potentially some breathing space, that we're not as close to rupture as is sometimes assumed".

However, those conclusions are being challenged by Canterbury University geologists, including two professors, head of department Jarg Pettinga and hazards and disaster management expert Tim Davies.

In a Perspective page article in today's Press, Davies said the "implication" of the research was "we can all relax and stop worrying about the Alpine Fault, because it might not cause a major earthquake for another 200 years".

Initial responses from the public to the study had been "largely sceptical" and agreed with the Canterbury University view that the report was "over-optimistic".

"Scientists and the media need to provide complete and accurate information to the public, but in this case the information appears to have been presented in an overly positive light," Davies said.

The information from trenches across the fault within 12km of Haast did not necessarily apply to motion on the rest of the fault.

Previous Alpine Fault quakes had ruptured only up to 400km of the fault, so might not have extended south of Haast to be recorded there, he said.

There was "strong evidence" that the 485-year average return period did not apply to the fault north of Haast.

"The evidence that the threat of a major alpine earthquake anywhere on the Alpine Fault has receded is, in fact, very weak."

The best approach was to accept the fault's next major quake could occur any time and to be prepared for that, Davies said.

Berryman had warned that the researchers' calculations were based on a rupture history of only the three most recent quakes they found evidence for — in 1717, 1230 (plus or minus 50 years) and 750 (plus or minus 50 years).

GNS Science researchers Kate Clark and Ursula Cochran yesterday received $311,000 from the Government's Natural Hazards Funding Platform to improve forecasting of large to great quakes on the southern part of the Alpine Fault.


http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/6734489/Alpine-quake-optimism-faulted-by-geologists
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« Reply #9 on: April 14, 2012, 03:28:12 pm »


Over-optimistic to a fault

When will there be an earthquake on the Alpine Fault? Tim Davies, Jarg Pettinga,
Carolyn Boulton, Greg de Pascale and Tom Robinson have been reviewing the data.


The Press | 11:53AM - Friday, 13 April 2012

ZEALANDIA CONTINENT.

ON APRIL O2, The Press reported that the threat of an Alpine Fault earthquake has decreased, based on data from trenches recently excavated across the fault south of Haast.

Instead of the previously accepted 200-to-300-year interval between these major earthquakes (M equals 8 or more, about 30 times the energy of the September 04, 2010, earthquake), the trenching shows that the interval is about 50 per cent longer; 485 years.

Since the most recent earthquake on the Alpine Fault occurred about 1717 (295 years ago, very close to the "old" recurrence interval), the implication is that we can all relax and stop worrying about the fault, because it might not cause a major earthquake for another 200 years.

It has become clear since September 04, 2010, that people want the best information they can get about earthquakes, so this good news should be welcomed widely.

However, initial responses from the public have been largely sceptical, and correspond to our own conclusions that the report is over-optimistic.

Scientists and the media need to provide complete and accurate information to the public but, in this case, the information appears to have been presented in an overly positive light, for the following reasons:

First, it applies information from trenches within 12 kilometres of Haast to the entire Alpine Fault.

The fault extends more than 600km from Milford Sound in the south to Blenheim in the north, so data from 2 per cent of this length may in fact tell us little about most of the fault's behaviour.

Previous individual Alpine Fault earthquakes have ruptured lengths no longer than about 400km, so may not extend to the south of Haast or be recorded there.

For example, there are independent records of large earthquakes north of Haast in 1717, circa 1625, circa 1425 circa 1300, circa 900, and circa 400 (as documented by Berryman et al in 2009) with a recurrence interval of about 300 years.

At Hokuri Creek, 100km south of Haast, 8000 years of records give a recurrence interval of about 320 years, according to a paper by Biasi, Clark, Berryman, Cochran and Prior presented to the American Geophysical Union in 2010.

The 485-year return interval from the Haast trench data evidently does not apply north or south of the site.

Second, the long-term tectonic slip rate (the rate at which the Pacific and Australian plates are sliding past one another), as calculated from the Haast trench data, is about 17 millimetres a year, about 50 per cent less than that on the rest of the fault.

On the central Alpine Fault between Haast and Hokitika, slip rates are 27mm, plus or minus 5mm a year (Norris & Cooper, 2001); in the Cascade area, 50km south of Haast, they are 23mm, plus or minus 2mm a year (Sutherland, Berryman and Norris, 2006); and, 80km further south at Milford Sound, the slip rate is about 26mm a year (Barnes, 2009).

The slip rate deficit from the Haast trenches suggests that some earthquakes may not have been recorded or identified there.

Thus, the average return interval of 485 years may apply to the limited area of the trenching, but there is some doubt about that; and there is strong evidence that it does not apply to the 300km of the Alpine Fault north of Haast.

The evidence that the threat of a major alpine earthquake anywhere on the Alpine Fault has receded is, in fact, very weak.

In any case, the question of overriding importance to the population and commerce of the South Island is not the average return period between earthquakes, but when the next major earthquake will occur.

It will occur at some unknown (but fixed) time in the future; the data referred to above indicate that it could happen today, or after some centuries, or at any moment in between.

Therefore, the most rational approach to the next major earthquake is to accept that it can occur at any time, and make preparations as soon as possible.

These range from stocking up with food and other supplies, all the way to reorganising society and commerce to be less vulnerable to the earthquake and its consequences, and thus better able to redevelop afterwards.

Some of these preparations can (and should) start immediately, but many will require gradual implementation; however, the sooner they begin, the less damaging the earthquake will be.

It is also vital to recognise that any Alpine Fault earthquake and its aftershocks will cause substantial disruption to the landscape.

Current research at the University of Canterbury shows there will be many large and small landslides, likely causing tsunami in lakes and fiords, landslide dams and dambreak floods in rivers, widespread aggradation and avulsion of rivers, and debris flows in small creeks, as a result of massive sediment inputs. These effects may continue to disrupt recovery efforts in alpine and adjacent regions for years to decades after the Alpine Fault earthquake.

This research into the magnitude of the earthquake and its effects is ongoing.

While the "threat" of an Alpine Fault earthquake may appear to have waned, that earthquake will still occur when it would have occurred anyway, irrespective of attempts to refine the statistical parameters of the fault.

It would be a serious mistake for authorities or public to breathe sighs of relief, in the belief that disaster has been postponed — it hasn't.


  • Tim Davies and Jarg Pettinga are professors in the Department of Geological Sciences, University of Canterbury;
    Davies leads the University's Hazard and Disaster Management programmes. Carolyn Boulton, Greg de Pascale
    and Tom Robinson are doctoral researchers at the University of Canterbury.

http://www.stuff.co.nz/the-press/opinion/perspective/6735254/Over-optimistic-to-a-fault
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« Reply #10 on: May 23, 2012, 07:44:20 pm »


Slowing moving quakes last 30 minutes

Fairfax NZ News | 2:06PM - Tuesday, 22 May 2012

HIGH ON A MOUNTAIN TOP: Carolin Boese and Aaron Wech at one of the testing stations in the Southern Alps.
HIGH ON A MOUNTAIN TOP: Carolin Boese and Aaron Wech
at one of the testing stations in the Southern Alps.


SLOW, creeping earthquakes lasting up to 30 minutes are taking place deep beneath the Alpine Fault on the South Island's West Coast, regarded as New Zealand's most hazardous fault line.

Scientists have been puzzled for decades by an apparent absence of earthquakes in the central section of the Alpine Fault, between Fox Glacier and Whataroa Valley 50km to the north.

But a study led by Victoria University Geophysics Professor Tim Stern found the area often experienced seismic tremor, or a series of slow, creeping earthquakes that each last up to 30 minutes.

It was not clear what the discovery meant for future earthquakes. He said it was not possible to accurately measure the small quakes for magnitude.

Dr Aaron Wech, a member of the Victoria University team, said it could be that constant tremors build up stress and may trigger a major fault movement or, alternatively, the activity may decrease the likelihood of a major quake by acting as a release valve for stress.

It was important to find out more about the tremor events, such as where they happened and how often, so the hazard posed by the Alpine Fault could be better predicted.

Wech, who previously researched seismic tremor in the United States, said the slow earthquakes did not cause damage, but knowing they were happening shed new light on activity in the Alpine Fault.

Stern said it was only the second time this type of seismic activity has been recorded on a strike-slip fault — those with walls that move sideways rather than up or down. The other was the San Andreas Fault in California.

Findings of the research, which received a $700,000 Marsden grant, were published today in American journal Geophysical Research Letters.

PhD candidate Carolin Boese led the field work which involved drilling holes up to 100 metres deep and installing sensors in them which vibrate when an earthquake takes place.

An array of 11 stations, called the Southern Alps Microearthquake Borehole Array — or SAMBA — was installed in late 2009 and is still producing data.

To date, SAMBA has recorded around 2500 small earthquakes which are taking place in a 30km-wide area under the Southern Alps, rather than on the Alpine Fault.

Conditions facing Boese and her assistants in installing and maintaining the stations included rain, snow, extreme temperature variations and strong winds.

Mountainous terrain was another challenge — with a 12-hour hike to and from one of the most remote sites, while kea showed constant interest in the equipment.

Stern said they hoped to expand SAMBA by adding new sites to record more small earthquakes and also to measure the seismic tremor over a longer period.


http://www.stuff.co.nz/science/6965606/Slowing-moving-quakes-last-30-minutes
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« Reply #11 on: June 28, 2012, 04:50:56 pm »


8000-year quake record improves understanding of Alpine Fault

With an elapsed time of about 295 years since the last big quake, a major earthquake in the
near future would not be a surprise. Equally it could be up to 100 years away. The bottom line
is – if not in our lifetimes then it is increasingly likely in our children’s or our grandchildren’s.
Therefore a precautionary approach is certainly warranted.
” — Dr Kelvin Berryman


THE ALPINE FAULT. — GNS SCIENCE.

MEDIA RELEASE - GNS SCIENCE | 12:25PM - Thursday, 28 June 2012

A GEOLOGICAL STUDY of the southern section of the Alpine Fault spanning the past 8000 years has given scientists an improved understanding of the behaviour of this major plate boundary fault.

The investigation, which was centred on a remote river terrace near Lake McKerrow about 35km northeast of Milford Sound, and supplemented with information from the Haast area, found evidence of 24 surface ruptures of the Alpine Fault dating back to 6000BC.

Scientists used a range of investigation techniques, including radiocarbon dating of seeds, leaves, and reeds contained in swampy sediments, to determine the ages of the ruptures.

The dating measurements were made at GNS Science’s Rafter Radiocarbon Laboratory in Lower Hutt.

The findings dramatically improve the known earthquake history of the Alpine Fault. Previously scientists had determined the ages for only the last four earthquakes dating back to about 1000AD.

The project has produced one of the longest continuous earthquake records of any on-land plate boundary fault in the world. Knowing the ages of so many major earthquakes enables a better understanding of the fault’s behaviour.

The investigation found the mean interval between large earthquakes on the fault is 330 years and two thirds of the intervals were between 260 and 400 years. As with many natural systems, there was a spread of intervals with the longest being about 510 years and the shortest about 140 years.


Hokuri Creek Location.An aerial view of the Alpine Fault at Lake McKerrow.

The Alpine Fault extends about 600km along the spine of the South Island between Milford Sound and Marlborough. When it ruptures, it produces an earthquake of about magnitude 8.0.

The study, published in Science this week, focuses on alternating peat and silt layers left as a signature from each of the surface ruptures of the fault. The scientists looked specifically at the timing of past earthquakes at the Lake McKerrow site and did not determine the length of surface rupture for these earthquakes.

The four-year research project was led by GNS Science and funded by the Marsden Fund, which is administered by the Royal Society of New Zealand. Other participants were from Victoria University of Wellington, as well as scientists from Italy, Israel, and the United States.

Recent studies have suggested that fault rupture occurs randomly or in clusters in response to a range of factors including interactions with other nearby faults. However, this study has shown that for faults similar to the Alpine Fault, a fairly regularly repeating earthquake cycle is a realistic foundation on which to base earthquake hazard estimates.

Based on this research, scientists have estimated there is a 30% probability of a large earthquake on the Alpine Fault in the next 50 years. This is at the higher end of existing estimates, which were based on only the last four large quakes on the fault. Scientists have more confidence in this new estimate as it is based on a much longer earthquake record.

“There is considerable interest in these new results given that earthquakes on the Alpine Fault pose a threat to large parts of the South Island,” said project co-leader Kelvin Berryman of GNS Science.

“On a national scale, we can now base our modelling on knowledge of the timing of 24 earthquakes compared to the four that were known prior to this investigation. This will greatly improve the reliability of earthquake hazard modelling,” Dr Berryman said.

“This research has particular significance to Canterbury where the findings are being incorporated in liquefaction and earthquake shaking mitigation measures as part of the rebuilding process.”


Kelvin Berryman and Ursula Cochran. — Photo: Margaret Low/GNS Science.
Kelvin Berryman and Ursula Cochran. — Photo: Margaret Low/GNS Science.

For project co-leader Ursula Cochran, also of GNS Science, the long earthquake record they uncovered highlighted the inevitability of a major earthquake occurring on the southern section of the Alpine Fault in the future.

“The last earthquake occurred about 295 years ago, so there is no better time than the present to prepare for the next one,” Dr Cochran said.

At the household level, these measures include emergency kits, anchoring furniture, removal of old-style chimneys, and family communication plans. At the local community level, measures could include planning for the care of the elderly and young if the community is isolated, and identifying skills and equipment helpful in a disaster.

At the local and regional government level, hazard mitigation policies in land use planning, strengthening earthquake-prone buildings and infrastructure, will reduce loss of lives and incomes.

“The more thorough the preparation, the lower the eventual impact will be,” Dr Cochran said.


______________________________________

Alpine Fault Q&A

1. What was the problem the scientists were trying to resolve with this project, and how did they go about it?

The biggest unknown at the start of this project, and for similar projects on many major faults worldwide, was the pattern of major earthquake recurrence. Do the major earthquakes occur randomly, regularly, or in clusters? The goal of this project was to determine the ages of as many past major earthquakes as possible. The scientists obtained a large number of high-resolution radiocarbon ages (about four per rupture) in an attempt to accurately date the past earthquakes preserved as abrupt changes in sediment layers at the study site. This is a high number of radiocarbon ages compared to other active fault investigations in New Zealand.

2. How does radiocarbon dating work in helping scientists understand the rupture behaviour of a major fault?

Scientists were able to radiocarbon date leaves and seeds that were buried by silt each time there was a major earthquake. The silt layers were deposited at the time of earthquakes when fault movement temporarily dammed Hokuri Creek and silt from river sediment was deposited on top of peaty sediment. The scientists could see striking alternations between peat and silt in the banks of Hokuri Creek and these sedimentary signatures of earthquakes extended back in time for 8000 years. They represented more than 20 fault movements and accompanying major earthquakes.

Ages of these major alternations show that the fault has ruptured regularly in the past - not like clockwork but not randomly or in clusters as is observed on some other faults. The shortest interval between quakes was about 140 years. The longest interval was about 510 years, with an average of 330 years.

3. Are these findings entirely new?

These findings are entirely new for the Alpine Fault. Prior to this project, the ages of only the last four Alpine Fault earthquakes were well known. Long records with more than 20 earthquakes have been obtained from other faults around the world such as the San Andreas Fault in California, but they are very rare. The Alpine fault is perhaps only the fifth such long record and it has revealed the most regular rupture behaviour yet reported.

4. What is the take-home message from this investigation?

Scientists have found a fault that responds to the steady motion of tectonic plates by rupturing at reasonably regular intervals. This illustrates that at least some plate boundary faults can be "well-behaved" when they are have high rates of movement and are not influenced by activity on other nearby faults. Based on this research, scientists have estimated there is a 30% probability of a large earthquake on the Alpine Fault in the next 50 years. This is at the higher end of existing estimates, which are based on only the last four large quakes on the fault. Scientists have more confidence in this new estimate as it is based on a much longer earthquake record.

5. Does ‘well behaved’ mean that scientists can predict the year, or decade, when the next rupture will occur?

No, unfortunately not. It simply means the Alpine Fault exhibits a fairly regular cycle of stress accumulation and rupture. It does not have long periods of more than 1000 years of inactivity. Equally, it does not have clusters of big earthquakes occurring at short intervals.

6. What are the wider implications of this work?

The research has important earthquake hazard implications nationally by providing a much longer record and therefore a more reliable forecast of when the next major earthquake will occur on the southern section of the Alpine Fault. The last major earthquake on the Alpine Fault occurred 295 years ago. As we are approaching the average time between ruptures — 330 years — there is no better time to get serious with mitigation and preparedness.

7. How might authorities use these findings in disaster planning?

Scientists have been communicating results of Alpine Fault research to authorities in New Zealand for many years. The current research results add confidence to the forecast of average repeat intervals of major earthquakes, the elapsed time since the last earthquake, and most-importantly the relatively regular repeat time. The important things for authorities are to encourage personal and household preparedness, to address earthquake-prone building occupancy in areas near to the fault, and to encourage preparedness actions among emergency services and responding agencies.

8. Is there a concern that the public might misinterpret these research findings?

The public might misinterpret these findings as a prediction — it is not. There is also a possibility of misinterpreting the results as the earthquake being imminent, which it may not be. The mean recurrence interval between the 24 earthquakes is about 330 years. So with an elapsed time of about 295 years since the last big quake, a major earthquake in the near future would not be a surprise. Equally it could be up to 100 years away. The bottom line is — if not in our lifetimes then it is increasingly likely in our children’s or our grandchildren’s. Therefore a precautionary approach is certainly warranted.

9. How do scientists account for the variability in rupture intervals — from 140 years to 510 years?

There are numerous factors that cause a fault to rupture that can change through time including rock strength, frictional properties of the fault plane, and transfer of stress from other nearby faults. Therefore, there will always be some natural variability in the timing of earthquakes. The results of this study show some of the most regular behaviour for faults worldwide indicating that there are few factors changing dramatically through time for this section of the Alpine Fault.

10. How representative is the southern section of the Alpine Fault (where this study was conducted) of the entire Alpine Fault?

Previous studies on the Alpine Fault indicate that some earthquakes have only ruptured northern parts of the fault, while others appear to have ruptured almost the entire length of the fault. This study did not investigate rupture length, so although scientists consider the earthquakes at Hokuri Creek were large enough to rupture much of the southern and central parts of the fault, they will not be certain of this until they can correlate with earthquake records at other sites. Work currently being done by NIWA on the offshore part of the fault, south of Milford Sound, may help to determine how far south such earthquake ruptures extended.

11. This research seems to reach a somewhat different conclusion to recent studies by other research teams. Why do scientists studying the same fault come to different conclusions?

Prior to this study, all estimates of the mean recurrence interval for the Alpine Fault were based on three or four past earthquakes. Estimating a mean from 24 ruptures is more reliable than previous studies. The dates of the four most recent earthquakes haven't changed, but this study has shown that the variability in recurrence in recent times is not representative of the variability over an 8000 year time frame.

12. Where might research go from here and what challenges do scientists face?

Scientists are keen to refine the timing of past earthquakes by further dating of the sediments. This would be followed by robust statistical analysis on the expanded collection of dates. However, there is no funding for this at present. Secondly, it is important to find other sites along the fault so that the results from a single site can be validated by results from other locations. It is a challenge to find appropriate sites where there are long records of past fault movements, and where it is possible to date sediments. The physical environment along the Alpine Fault is very challenging with annual rainfall of 5-8 metres and steep slopes that are prone to landsliding, which obscures the fault in many locations. There is also thick rainforest that makes access difficult and fast-flowing rivers carrying coarse gravel that is difficult to date.

13. Is this research peer-reviewed?

The research underwent exhaustive international peer review. Science is a highly reputable international journal and it publishes fewer than 10% of research papers it receives.


http://www.gns.cri.nz/Home/News-and-Events/Media-Releases/improved-understanding-of-alpine-fault
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« Reply #12 on: August 01, 2012, 01:36:58 am »


Post-quake preparedness a priority for town

One of the important lessons from the Canterbury earthquakes has been that the impact
on communities goes far beyond lives saved or lost. JOHN McCRONE reports.


The Press | 10:50AM - Saturday, 28 July 2012

IN THE FIRING LINE: Franz Josef township's main road.
IN THE FIRING LINE: Franz Josef township's main road.

WOULD YOU build a petrol station and motel right on top of an earthquake fault? And not just any old crack in the ground, but straddling the magnitude 8 Alpine Fault?

Franz Josef township on the West Coast highway must surely take the prize as the single most hazardous spot to live in New Zealand. The Alpine Fault cuts straight through the very centre of this glacier country tourist stopover.

When the fault goes — and it is only a matter of time — the town will literally be ripped in two, the separate halves travelling nine metres in opposite directions at a rate of knots.

Not good news for the Allied service station, Alpine Glacier motel or any of the other buildings sitting directly astride the gap. Nor that great for those built up to its lip, such as the police station that was put up just a few years ago.

So what is Franz Josef to do? Move back a decent distance, entirely relocate, cross its fingers and trust the Alpine Fault holds out for another few generations, making it someone else's problem? The current odds are 30 per cent the fault will rupture in the next 50 years.

The town has of course known for a long time that it is bisected by the fault running the length of the South Island — but anecdotally rather than officially, says GNS Science earthquake hazard expert Robert Langridge.

It has not been written into local maps and planning policies he says, so people have been allowed to continue building across it even during the past 15 years. "I've been on several field trips with a car-load of geologists and we go, ‘Aw yeah, the fault runs right through the petrol station’. And then we kind of chuckle. But on the other hand, we know it's not really acceptable," says Langridge.

The township has some hard decisions to make now that Langridge has delivered a blunt language report about exactly how exposed its residents and visitors actually are.

Langridge says the issues go beyond simply the risk to life if the petrol station is torn apart. After the big one, Franz Josef could be isolated for months by landslips, broken bridges and re-routed rivers.

"In terms of post-disaster preparedness, you've got to have a petrol station that is functioning so that people can get on with filling up their diggers and vehicles." It is serious stuff. And Franz Josef is a microcosm of what is happening throughout New Zealand since the Canterbury earthquakes.

We always knew we lived on the shaky islands, but now the actual experience of a worst case scenario disaster is forcing a re- examination of the hazards to which we may have been guilty of turning a blind eye.

In Tekapo, for example, locals are looking at their sweeping foreshore — a tempting spot for town expansion — and realising that it has been probably carved out by mini-tsunamis, the slopping of the lake, when the Alpine Fault ruptures every 330 years or so.

In Wellington, a new Civil Defence report has pointed out that with just two hilly highways in, the city could be cut off for up to four months by a decent shake.

Christchurch was fortunate in being a flat city, ringed by access roads. Help could arrive from all directions, services could be swiftly reconnected, people and businesses were able to relocate. The same earthquakes in Wellington would likely force a mass evacuation, creating a far more permanent economic devastation.


GNS Science's Kelvin Berryman.
GNS Science's Kelvin Berryman.

GNS Science's Kelvin Berryman, manager of the national Natural Hazards Research Platform, says New Zealand has perhaps been rather lulled because it has been so long since a really major destructive event like Napier.

"Institutionally, we've probably forgotten some of the lessons because there's been 50 years of fairly benign earthquake activity," he says.

However, scientists like himself now have people's attention. And as the information continues to pour out about what actually happened in Canterbury — how the land behaved, how people responded - the understanding of quake hazards can be that much more fine-tuned.

"To be realistic, the honeymoon period where earthquake hazards are going to be in the front of everybody's minds is going to be very short. We'll be overtaken by other events before long. But at least there's a window of about two or three years to embed some better processes around the country," Berryman says.

The Canterbury earthquakes are certainly still yielding up their secrets.

Canterbury University's head of geology Professor Jarg Pettinga says they will be about the best understood anywhere because in the 1990s a former university seismic engineer, John Berrill, installed a network of ground motion sensors right across Christchurch and out into the surrounding Canterbury Plains.

The network of 30 accelerographs was there waiting to record the Alpine Fault, but ended up perfectly placed to capture everything that has happened over the past two years. So along with the satellite imagery and other evidence, there is a huge volume of data to be analysed and gradually a very detailed picture is emerging.

For instance, says Pettinga, recent 3-D modelling by an Oxford University collaboration has found that the original September 2010 Darfield earthquake was not the result of a single fault, but a chain reaction of some eight fault segments that unzipped in quick succession.

The first to go was a cross-wise section, the Charing Cross Fault, that by itself would have amounted to only about a 6.5 shake.

But this then pressed on the centre of a complex line of fracture — the Greendale Fault — running down from the Canterbury foothills towards Christchurch, triggering a cascade to both east and west which built to a magnitude 7.1 earthquake until either the energy was spent or the faulting was halted by a change in terrain.

Pettinga says the Alpine Fault — the crunching joint between the Pacific and Australian continental plates — is a single frequently polished break. It fractures often enough to be worn smooth. This is why it is possible to point to the individual buildings in Franz Josef which are bang in its firing line.

The Canterbury Plains however are a maze of ancient fissures and folds that get loaded up with the twisting lateral strain the Alpine Fault exerts on the whole east coast of the South Island. The Alpine Fault disperses about 75 per cent of the seismic energy and the other 25 per cent goes into generating local earthquakes.

"Over geologic periods of time, these Canterbury Plain faults will get some width associated with them because they will sometimes rupture on one bit, sometimes on a different plane right next to it." Pettinga says the modelling now suggests the February 22 Port Hills earthquake was produced by a linking up of three fault segments, June 13th's 6.3 was the result of another pair, and then December 23rd's 5.8 off New Brighton Beach was just a single fault.

Pettinga fingers its dotted trace on the map. You can see how last December's is now looking like a seaward continuation of the CBD Fault — the buried line found after a seismic survey last year which alarmingly runs all the way under the central city from Riccarton out to Aranui and New Brighton beach.

This section stirred on Boxing Day 2010 with a sharp 4.9 shake, yet thankfully switched off again following February 22nd. "The rupture of the Port Hills Fault did seem to relieve the stresses in the city area as it has gone dormant since then," says Pettinga.

However, it does appear to have been a narrow escape. "It is looking as though the two sections are lined up — they may be two branches of a historic fault lying quite close to each other, but not quite linked." In hindsight, if both had lit up together, there was the potential for a February-level quake even more directly under tall buildings and centres of population, Pettinga admits.

On a positive note, the energy unleashed by the Darfield earthquake does now seem to have worked itself across Christchurch and safely out into Pegasus Bay, he says. And once any local faults have gone, it will take thousands of years to build up the same levels of strain again.

It is this kind of fine detail about how the land has behaved that is going to be so useful in judging earthquake hazards in the future, Pettinga says.

For example, knowing how the stresses of one quake radiates through the ground to trigger another much further away could well have given Christchurch warning of what was to come after Darfield.

"Because we've got this world-class recording system in place, we've got an incredible record of the seismicity over some 22 months."

"We've captured the aftershock data with a high degree of precision and we can now back- analyse to see whether future stress modelling may allow us to do a much better job in terms of forecasting what will happen over a period of months in a large earthquake event." Probably even more valuable will be the ability to match the strength of shaking to the actual topography of the ground.

Pettinga says one thing learned is the way the aquifer under Christchurch International Airport acted as somewhat of a trampoline shock absorber for that area. And by contrast, how other landscape features, such as the ridgelines of the Port Hills and its loose sediment filled basins, worked to focus the energy of the earthquakes.

A sudden slowing and bunching of the shock waves as they passed from hard rock to unconsolidated gravel was the reason the Heathcote Valley suffered the most off-the-scale ground accelerations in February, says Pettinga.

"In the future, we should be able to identify areas prone to very strong ground shaking due to these kind of particular site effects," he says.

There could be a micro-zoning of a city based on this knowledge, a fine-tuning of building codes that would make New Zealand cities both safer, and also save money because the precautions could be more closely tied to the actual levels of risk.

GNS's Berryman says the Canterbury experience has definitely created some new questions. The cascade effect is one that seismologists want to understand better — especially in relation to the Alpine Fault.

Knowledge about the Alpine Fault itself tightened up recently with the June publication of a paper by a team led by Berryman. The group managed to find a hillside by a creek near Milford Sound that bore the marks of 24 Alpine Fault quakes dating all the way back to 6000BC.

Berryman says this continuous record shows the fault indeed keeps to a remarkably regular schedule. The average time between movements is 330 years, with two-thirds of all the quakes happening within 260 to 400 years.

The smallest gap was just 140 years, the longest stretched out to 510 years. But with the last earthquake taking place in 1717, this is why the current odds of another stands at 30 per cent within the next 50 years.

Berryman says a lot of people's thinking has been focused on the immediate impact of a magnitude 8 earthquake — what it will be like for Queenstown, Franz Josef, Hokitika and others most likely to be hardest hit. But now there is the further worry of the chain reaction that perhaps should be expected.

Depending on which direction the fault breaks, says Berryman, it will load up the landscape with an energy that will have to be dispersed in a series of knock-on events.

"If it ruptures North to South towards Milford Sound, then that's bad news for Fiordland. Most of the forward energy will be directed down there. But if it ruptures from South to North, then it will impose an additional stress to the ends of all the Marlborough faults." So quite possibly, in the same way that the Darfield earthquake has triggered a sequence fanning out into Pegasus Bay, this could cause a succession of large earthquakes through Kaikoura, Blenheim and other areas lasting 40 or 50 years, Berryman says.

The point is not to worry people, but to have good information on which to base decisions. And right now, geologists are not even sure which direction the Alpine Fault normally does break.

Berryman says as much as learning about the way the land reacts, an important lesson from Canterbury has been realising the potential social and business costs of a major event.

He says the old hazard models emphasised saving lives and strengthening individual buildings. Now there is a need to consider the effects on whole communities and the national economy — how to minimise the costs and disruption of a recovery. "It's been a huge wake-up call that has certainly sparked a whole bunch of thinking around economic resilience."

Berryman says such has been the shock of the quakes that in some quarters he is seeing almost an over-reaction. "We've now got some officials worrying about liquefaction and weak soils in their cities where they haven't really got the level of earthquake risk to make it a problem."

Or the fears need some calibration. Wellington has become so dominated by its talk about really big earthquakes, says Berryman, that it is possibly not paying enough attention to the more likely medium-scale ones that would still cause serious disruption.

Likewise, Auckland is thinking about its volcanoes. However, from a risk-modelling point of view, maybe there should be more concern about the virtual certainty of Mount Ruapehu going again sometime soon.

"Ruapehu has an average 20-year return for a 1995 style eruption, and every 100 years you are going to get something even more significant. Imagine the ash coming out of that and a southerly heading towards Auckland. If you had to close down the airport for a long time, the economic impact could be pretty serious."

Yet generally the Canterbury earthquakes are being correctly heeded, says Berryman. He sees changes being made that are building in a preparedness for all kinds of natural hazards.

"Some people may be just thinking about translating ‘earthquake’ all around the country. But it's irrelevant what kind of event it is if it's potentially economy-changing. The resilience implications are much the same whether it's mega-floods, tsunamis, volcanoes or even biosecurity."

So how is Franz Josef going to respond to its own specific dilemma?

Franz Josef Community Forum chair Marcel Fekkes, who runs luxury villas at the entrance to the glacier field, says as you can imagine there are some rather delicate negotiations taking place with the Westland District Council and other local authorities.

The problem is the risks were known, but never properly recognised. "The police station was built only three years ago, but they put that right by the fault line as well." Fekkes says the question now is what kind of solution will be acceptable — and who pays?

Langridge's report suggests a number of options, the most extreme being to abandon the town completely and move its people elsewhere. But a minimum plan is to create a fault avoidance zone (FAZ), a safety corridor some 200 metres wide, and gradually shift people back from the edge.

"It'll be like being red-stickered, but allowed to stay in the buildings," says Fekkes. And town opinions are divided about this.

"Due to events in Christchurch, everyone has got a little more panicky about the risks," he says. Yet faced with the prospect of having their properties blighted without any official recompense, many also would rather the whole subject was quietly dropped. 'For some, the best option is just to forget about it, I think.'

Fekkes says the hope is the local council will eventually accept blame for not preventing development and so come to the table with financial assistance to shift the petrol station and buy out the other properties. 'This whole process could take a couple of years,' he says.

GNS's Langridge says Franz Josef's case is certainly a tough one. But as the ripples from Canterbury's experience continue to spread, he is seeing fewer excuses, a greater willingness to respond to information about New Zealand's natural hazards.

"Yes, people are kind of accepting that what these scientists have been going on about for all these years might actually have something to it now."


http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/7367350/Alpine-Fault-poses-threat-to-Franz-Josef
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« Reply #13 on: August 18, 2012, 11:56:55 pm »


Alpine Fault to be mapped

By REBEKAH FRASER - The Greymouth Star | Friday, 17 August 2012

ALPINE FAULT

WESTLAND RESIDENTS will soon be able to see exactly where the Alpine Fault cuts through the district.

Maps showing the location of the faultline are being drawn up and should be available through the Westland District Council by the end of next week.

District planner Rebecca Beaumont said about 20 maps covering the entire district would be available as the council moves ahead with a plan to create a fault avoidance zone (FAZ) at Franz Josef Glacier township.

“The proposed plan change, to create the zone, should be notified by the end of next week and the maps will be linked on council’s website.”

The FAZ is being created after surveys showed the faultline runs straight through the Franz Josef Glacier township.

Mrs Beaumont said Franz was the only built-up area in Westland that the fault ran directly through.

“There are one or two other structures that the faultline runs through, but the majority is land.”

The council plans to create the zone with a corridor 120m to 140m either side of the faultline. No new buildings will be allowed to be built within that zone. Existing users could be able to modify their buildings in certain circumstances, but no extensions will be permitted.

Existing residents and businesses within the zone will also not be able to “change or increase in an activity”, meaning that somebody wanting to convert a motel to a cafe, or something similar, could also be turned down.

The FAZ could impact those in the Franz Josef community pushing ahead with an “urban revitalisation” plan.

Franz Inc has developed plans to rejuvenate the village, including suggesting that lightweight single-storey commercial buildings could be built within the zone.

The council strategy committee considered the plans at its quarterly meeting yesterday.

Mrs Beaumont told the committee the plans would be in “potential conflict” with the council’s proposed plan change.

“However, I quite like the idea of a walkway along the faultline, it’s undeveloped and what we are looking for.”

Franz Inc plans also include a new “river gateway” walkway from the town centre to the river, new car parking and a new flight centre, and a “pedestrian precinct” in Cowan Street.

Mayor Maureen Pugh commended the community for the ideas.

“It is great to see that the community has shown leadership in planning for its future.”


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« Reply #14 on: August 29, 2012, 02:45:36 pm »


Quake-zone plan moves ahead

By REBEKAH FRASER - The Greymouth Star | Monday, 27 August 2012



THE ALPINE FAULT may soon restrict where new buildings are able to be erected, as the Westland District Council pushes ahead with plans to create a district-wide ‘fault avoidance zone’.

It hopes to create two new zones along the length of the faultline — one for Westland and a more specific one for Franz Josef Glacier village — as it looks to manage the risk from a fault rupture.

It will see an area of land between 20m and 200m either side of the faultline being blocked out with building restrictions.

Plans for the fault zone, which was created and mapped by the Institute of Geological and Nuclear Sciences, have been released and are now out for public consultation.

The council said an earthquake event on the Alpine Fault would create “a number of significant processes” within Westland.

“Any building or structure affected by fault rupture is likely to suffer considerable damage. This in turn puts lives at risk.”

It will now ask landowners within the general zone to provide additional technical reports in order to establish a more precise location of the faultline.

In the general zone, residential buildings will be discouraged, but agricultural and forestry activities, including buildings not used for residential activities, could be permitted.

The council would also include the zone on its Land Information Memorandum (LIM) reports, and those applying for a building consent within the zone would need to have a statement from a qualified engineer that the building would perform post-fault rupture.

“In the council’s view, this certification may be difficult to obtain.”

It said extensive studies had already been done in Franz Josef Glacier so the faultline mapping was already accurate.

“The rules within this area — the Franz Josef-Waiau fault rupture avoidance zone — are more restrictive.”

No new buildings will be allowed to be built within that zone. Existing users might be able to modify their buildings in certain circumstances, but no extensions will be permitted.

Existing residents and businesses within the zone will also not be able to “change or increase in an activity” — that clause would mean somebody wanting to convert a motel to a cafe, or something similar, could also be turned down.

GNS studies conclude that the probability of an Alpine Fault earthquake event, with fault rupture, occurring is 20% within the next 30 years.

Maps for the entire Westland district showing the location of the fault, are available through the council website. Franz Josef Glacier is the only built-up area through which the fault runs directly.

Submissions on the plan change close on September 24. Submissions received will then be summarised and put out again for consultation, followed by a hearing.


http://www.greystar.co.nz/content/quake-zone-plan-moves-ahead



Westland District Plan — Maps (7.45MB PDF document)

Mapping And Fault Rupture Avoidance Zonation (2.29MB PDF document)

Planning For A Safer Franz Josef/Waiau Community (1.68MB PDF document)



Franz fears ‘ghetto’

By CHRISTINE LINNELL - The Greymouth Star | Tuesday, 28 August 2012



FRANZ JOSEF GLACIER residents fear the West Coast’s main tourist town will become “ghetto-like” if the Westland District Council forges ahead with controversial plans to avoid the Alpine Fault, which runs through the middle of the village.

The council has notified a District Plan change to establish ‘fault rupture avoidance zones’ in areas closest to the faultline. Inside the zones, new building or building expansion would be halted, “due to the risk of human safety”.

The plan change also provides new building zones to the north of the existing township.

Marcel Fekkes, who chairs the business group Franz Inc., said 32 commercial and residential buildings were situated near the faultline.

“People won’t be investing in their properties because their buildings aren’t worth anything any more. It actually does create quite a problem for us.”

The council report says “any building or structure affected by fault rupture is likely to suffer considerable damage” which would put lives in danger.

According to research from GNS Science, Franz Josef village is “by far the largest community” built along the trace of the Alpine Fault, which crosses the town from the north-east to the south-west, including cutting straight through the service station on the main street.

The predicted movement was 8m to 9m horizontally and 1m to 2m vertically.

Council planning and regulatory manager Richard Simpson said the council had made a courageous decision.

“They have received some information, and instead of putting it in the too-hard basket or thinking ‘There’s a whole lot of houses there, what about the poor people,’ they have actually made a decision.”

While residents in Franz Josef seemed upset, most of the feedback from elsewhere in the district regarding the Alpine Fault had been positive. “Information actually provides certainty, and certainty is appreciated.”

But in Franz Josef, Fern Grove Supermarket owner Chris Roy said the proposed restrictions on building renovations would put his business in limbo.

“We’ve already got full architect plans for a whole new supermarket, which would be probably half as big again out the back.”

He spoke regularly to other business owners in the village and they had similar concerns about relocating the town.

He was also concerned that media coverage of the issue would drive away customers, 80% of whom were tourists or visitors.

The plan change was “all a knee-jerk reaction from Christchurch”, Mr Roy said.

“If we do get an earthquake here we’ll get a larger effect sitting on the faultline. But would it actually matter where you move to?

“I don’t think you would be safe on that whole area if we do get what they’re predicting.”

Mr Fekkes said that while he could understand the council needed to follow the GNS Science report, he did not think it was an exact science.

Responding to earlier comments from Mr Simpson that some buildings had “reached their economic life anyway”, he said, “There might be one or two that fit that description, but there’s a lot in there that certainly don’t.”

If the council could not help businesses financially, it should use its contacts in Parliament, he said.

“I think it should be on the council to find those funds for us. One way or another we do need assistance here.”

Meetings with affected parties were being organised this week and early next week. The proposed plan change is open for public submissions until September 24.

Mr Simpson said it was likely the businesses caught in the avoidance zone “are going to be run down” but said it was not the council’s responsibility to provide financial support.

Questioning the importance of the risk zones was “missing the point entirely”, he said.

“It’s the difference between a shaken martini and a stirred martini. Everything that is in the fault hazard avoidance zone is more likely to move and rupture, both horizontally and vertically.”


http://www.greystar.co.nz/content/franz-fears-%E2%80%98ghetto%E2%80%99
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« Reply #15 on: August 29, 2012, 04:36:27 pm »


Editorial: Own up to our faults

The Press | Wednesday, 29 August 2012

AT CENTRE: The Alpine Fault splits Franz Josef village in two, running through the forecourt of this petrol station and across the main highway. — Photo: PAUL GORMAN.
AT CENTRE: The Alpine Fault splits Franz Josef village in two, running through the forecourt
of this petrol station and across the main highway. — Photo: PAUL GORMAN.


THE fact that the little West Coast town of Franz Josef is built on the Alpine Fault has been known for years. Despite this, people there have managed to put it in the back of their minds and have continued to develop there almost as though the fault did not exist.

Last week that changed with the public notification by the Westland District Council of its intention to alter its district plan to prevent development where the risk is greatest. Critics of the move complain that it will ruin their businesses and sentence the town to a slow decline. That is very likely true but the council's move is merely belated recognition of reality and failure to act would be dangerously complacent.

The district council's plan is recognition of the high risk to the region created by the Alpine Fault. The fault has been marked by large-scale ruptures on a remarkably regular pattern, on average once every 330 years. The last big quake on the fault occurred in 1717 which enables geologists to calculate that there is a roughly 30 per cent chance there will be another major event within the next 50 years. It is a risk that cannot be ignored.

The district council's plan will create two new zones — the Franz Josef/Waiau fault rupture avoidance zone and the general fault rupture avoidance zone. The Franz Josef zone creates a 135-metre-wide swathe through the town where landowners will be able to carry on their existing activities but will be prevented from erecting new buildings, extending their properties or developing new subdivisions.

It is necessary because Franz Josef is right on the fault line. The town's service station, a motel and other buildings sit directly astride the gap. Although geologists, local politicians, residents and others have been aware of the dangers, it has not been written into local maps or planning policies, with the result that building across the fault has continued even during the past 15 years. The police station, put up only a few years ago, is right on the lip of it.

According to two recent GNS Science reports, a rupture of the fault could be expected to move the land up to 9m horizontally and 2m vertically. As Christchurch residents are well aware, movements of that magnitude would be catastrophic.

New Zealand has always been known as a seismically active landscape but the absence until September 4th, 2010, of any large urban tremors since the Napier earthquake in 1931 had enabled it to be treated at the level of mildly flippant remarks about the "shaky isles" and a less than rigorous approach to making buildings that were earthquake resistant.

Complacency had crept in and proved hard to eradicate. Even after September 4th, many objected when the Christchurch City Council tightened the building code to take account of the sharply exposed reality that this is an earthquake-prone country.

Franz Josef is not the only area in which risks that have for too long been ignored are now being properly recognised. Wellington, too, sits on a fault line and new assessments of the hazards created by old buildings are causing dismay to some property owners. The reassessments are unavoidable, however. As Canterbury's experience has shown, the risk does not disappear by being ignored.


http://www.stuff.co.nz/the-press/opinion/editorials/7565436/Editorial-Own-up-to-our-faults
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« Reply #16 on: September 18, 2012, 01:30:37 am »


Franz Josef asks for fault-line compensation

ONE News - TVNZ | 7:01PM - Monday, 17 September 2012

The fault line running beneath Franz Josef. — ONE News/TVNZ.
The fault line running beneath Franz Josef.
 — ONE News/TVNZ.


THE Westland District Council is proposing tough new limits on building development in Franz Josef — a plan that business owners say would penalise them unfairly.

Franz Josef sits astride the South Island's Alpine Fault line and affected business are planning on asking the government for compensation after the exact location of the fault — running under homes, a motel and a petrol station - was mapped.

Richard Simpson from the Westland District Council said: "There is a big risk of the Alpine Fault moving and any building within that fault area will break, will get destroyed and will fall down."

GNS scientists predict there is a 20% chance of the alpine fault rupturing within the next 30 years. If that happens, the ground could shift horizontally by up to nine metres and vertically but up to two metres.

The council is now seeking a ban on future development in areas which are close to the fault.

Simpson said the council was prepared to allow those people who are there already to stay. "But please no more, enough is enough already," he said.

It wants 38 buildings to comply with strict new guidelines, but business owners argue those rules would leave many out of pocket.

Marcel Fekkes from the Franz Josef Development Society said "if you can't do anything to your business then it wont have much value".

Government real estate is also at risk — including the police station and Department of Conservation houses.

Waynne Costello from DOC said they would like to see residents "move away from the zone completely" — a wish shared by affected business owners who want the government to help.

"The community would like to talk to the government to see if we can find a way similar to Christchurch landowners to find compensation for people in the zone," Fekkes said.

But the Ministry for the Environment says there are no compensation provisions under the Resource Management Act.

The town is now considering legal action.


Franz Josef business owners call for compensation (TVNZ On Demand news video clip - 2min 02sec)

http://tvnz.co.nz/national-news/franz-josef-asks-fault-line-compensation-5089325
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« Reply #17 on: April 11, 2013, 02:27:43 pm »


Dire quake warning for Alpine Fault

By SHELLEY ROBINSON - The New Zealand Herald | 9:40AM - Wednesday, April 10, 2013



CIVIL DEFENCE officials say there could be up to 10,000 casualties when the Alpine Fault ruptures — and 1000 could be fatal.

The West Coast would suffer most of those casualties and Christchurch will be relatively unscathed in comparison.

The figures have been revealed by Civil Defence emergency management group leader James Thompson, as Civil Defence, hospitals, police and other emergency services plan for a major exercise to prepare for The Big One.

The Alpine Fault is expected to rupture within 50 years, a one-in-500 year event that will produce a devastating earthquake of a magnitude 8 or more.

Towns and cities throughout the South Island will feel its tremendous power, with those on the West Coast taking most of its brunt.

Settlements and possibly towns are expected to be cut off for long periods because of landslides and wrecked roading and other links.

The predictions come as Civil Defence and emergency services across the South Island wait for the release of a Canterbury University study into the effects of the Alpine fault quake.

It will form the basis of a major South Island-wide Civil Defence exercise on May 29th.




The study is being carried out by Canterbury University geological sciences student, Tom Robinson, who is examining what will happen when the Alpine fault ruptures.

The mock disaster has been called "Exercise Te Ripa Hapa" (loosely translated as "Alpine fault earthquake") and will be activated in Marlborough, Nelson-Tasman, West Coast, Canterbury, Southland and Otago.

Mr Thompson said the force of the quake for Christchurch people would be similar to the 7.1 magnitude September 4th, 2010 event.

"It is expected that this would be more of a rolling earthquake which could continue for up to one or two minutes," he said.

Mr Thompson said he would expect serious disruption to roading in Canterbury, including rock falls which would cut off the Arthur's Pass and Lewis Pass with disruption to power and telecommunications.

City council unit manager for Civil Defence Murray Sinclair said he didn't expect building collapses like the February quake in Christchurch, but said unstable rocks on the Port Hills could present a problem.

Mr Thomson said a real rupture of the Alpine Fault was a reality.

"It is always a challenge to do this type of scenario as you don't want to cause alarm bells, but this is a reality. It is a case of not if but when. It is better if we are prepared," he said.


http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10876550
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« Reply #18 on: March 20, 2014, 01:32:41 pm »


Alpine Fault not so ‘well behaved’

By PAUL GORMAN - The Press | 5:00AM - Thursday, 20 March 2014

ALPINE FAULT: An 800 kilometre-long fault which runs along the western edge of the Southern Alps from Marlborough to Milford Sound. — GNS Science.
ALPINE FAULT: An 800 kilometre-long fault which runs along the western edge of the Southern Alps
from Marlborough to Milford Sound. — GNS Science.


THE ALPINE FAULT may have generated more large earthquakes than previously thought, making it increasingly dangerous in future, new research says.

Scientists have traditionally compared the fault to a metronome because of its apparent regularity in causing earthquakes around magnitude 8.0 every 300 years or so on average.

But University of Canterbury researchers have discovered signs that West Coast quakes — mostly blamed on the Alpine Fault — may not be as "well behaved" and regular as assumed.

They found higher "slip release rates" than might be expected based on existing Alpine Fault records, of an average 7.1 metres +/- 2.1m of ground movement in each event, meaning either:

• Moderate to large partial ruptures of the fault, generating quakes of magnitude 6.5 or higher, occur between the "great" magnitude 7.9 or larger quakes; or:

• Some of the quakes previously attributed to the Alpine Fault actually occurred on other faults.

Evidence of offsets along the fault was uncovered in dense bush using lidar (light detection and ranging), which strips away vegetation to reveal the landscape.

The Alpine Fault runs hundreds of kilometres along the western Alps from Marlborough to Milford Sound, where it heads offshore, and marks the Pacific and Australian plate boundary.

Researchers agree the last great Alpine Fault quake of magnitude 8.0-8.2 occurred in 1717, rupturing the ground's surface along more than 300km of the fault.

In comparison, the Greendale Fault that ruptured on September 4th, 2010, is about 30km long.

In light of their findings, another large quake around 1600, previously thought to be another great shake of similar size to 1717, now appears to be a partial rupture of magnitude of 6.5 to 7.0, or was even perhaps from another fault.

The most recent quake causing serious shaking on the Coast was about 1826 of magnitude 7.5.

A major Alpine Fault quake would cause significant damage on the Coast, block road passes for months, destroy infrastructure and generate several minutes of ground motion in Christchurch leading to liquefaction.

The research by Dr Greg De Pascale was published in Geology.

De Pascale's work over four years included periods in thick bush searching for ruptures.

He said lidar data had allowed him and collaborators Associate Professor Mark Quigley and Professor Tim Davies to find features, including streams and rivers, offset by fault movement.

They discovered the 1717 great quake caused about 7.5m of offset over about 380km of the fault. Previous research relied on dating material from trenches dug across the fault, as well as rockfalls and lake records, to estimate the size and year of quakes.

De Pascale said the conclusions were crucial for risk awareness.

"It suggests Alpine Fault quakes may be more frequent than previously suggested and less like clockwork every 300 years or so."

"Previous understanding suggested that after the next major Alpine Fault earthquake we can recover and relax for another, say, 200 to 480 years after the aftershocks cease. Our new findings suggest this may not be the case."

"The next major quake may only be a partial rupture on the Alpine Fault and so there may be another large earthquake following this. This suggests an increased hazard."


http://www.stuff.co.nz/the-press/news/christchurch-earthquake-2011/9846698/Alpine-Fault-not-so-well-behaved
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« Reply #19 on: May 21, 2015, 10:04:50 pm »


from The Press....

Franz Josef earthquake plan gets go ahead

By SARAH-JANE O'CONNOR | 3:51PM - Monday, 18 May 2015

Mapping has shown the Alpine Fault runs directly under some Franz Josef businesses, including the Mobil petrol station, the Helicopter Line offices and part of the supermarket. — Photo: Sarah-Jane O'Connor.
Mapping has shown the Alpine Fault runs directly under some Franz Josef businesses, including
the Mobil petrol station, the Helicopter Line offices and part of the supermarket.
 — Photo: Sarah-Jane O'Connor.


A PLAN to manage earthquake risk in a busy West Coast tourist town has been given the go ahead by commissioners.

Franz Josef is the only town to straddle the Alpine Fault. The Westland District Council has proposed a fault avoidance zone, 100 metres either side of the fault, running through the middle of the town.

Building consents within the zone would have to meet more rigorous standards and changes made to existing buildings would be limited.

Independent commissioners Gary Rae and John Lumsden accepted the change to the district plan, following a hearing in March.

Business owners told the pair they felt they were effectively being red-zoned and feared they would not be compensated if they had to relocate.

The Franz Josef zone includes 30 properties, including the police station, petrol station, supermarket and a motel.

On Monday, the council said commissioners had accepted the plan change with some amendments.

Buildings that had a “low consequence” of failure, such as small storage sheds, fences and in-ground swimming pools, would be exempt.

Prospecting, vegetation clearance and mining activities would not have further restrictions.


The Waiho River, near Franz Josef, in flood in May. Flood-prone businesses were relocated from its banks in 2003 and compensated. — Photo: NZTA.
The Waiho River, near Franz Josef, in
flood in May. Flood-prone businesses
were relocated from its banks in
2003 and compensated.
 — Photo: NZTA.


The plan change was publicly notified in August 2012 but staffing issues at the council meant progress was delayed.

Westland District Mayor Mike Havill said the Franz Josef community had been waiting for a decision for “some time, so that it can move forward with some certainty”.

Submitters have until June 30th to appeal the decision through the Environment Court.

Geologists estimate the Alpine Fault ruptures on average every 300 years, producing a magnitude 7-8 earthquake when it does. The last time it shook was 298 years ago.

The Helicopter Line general manager Grant Bisset told the commissioners in March that if the science was correct, then a bigger solution was required to manage long-term risk.

Several business owners said compensation should be on offer to help them move out of the zone.

In 2003, local authorities and central government contributed $2 million to relocate flood-prone businesses on the south bank of the Waiho River, on the outskirts of Franz Josef.


Related stories:

 • ‘Red-sticker’ fears for West Coast town

 • Franz Josef locals in limbo over fault plan

 • When, not if: Alpine fault could cause 8 metres of movement


http://www.stuff.co.nz/the-press/news/west-coast/68639125/franz-josef-earthquake-plan-gets-go-ahead
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« Reply #20 on: March 09, 2016, 10:55:14 pm »


from Fairfax NZ....

Alpine Fault moves more than any other known land fault in the world

Scientists make a sobering revelation: the Alpine Fault moves more than any other known fault on land.

By MICHAEL DALY | 3:08PM - Tuesday, 08 March 2016

The Alpine Fault, which runs up the spine of the South Island, has ruptured five times in the past 1,100 years — producing an earthquake of between magnitude 7 and 8 each time. — Picture: GNS Science.
The Alpine Fault, which runs up the spine of the South Island, has ruptured five times in the
past 1,100 years — producing an earthquake of between magnitude 7 and 8 each time.
 — Picture: GNS Science.


THE Alpine Fault has moved much more than previously thought, and more than any other known fault on land in the world, new research shows.

In the past 25 million years, the two sides of the South Island have shifted more than 700 kilometres relative to each other along the Alpine Fault. That is 250km more than previously thought.

The full extent of the movement was masked because the rocks first moved 250km in one direction, then went back the other way — retracing the first 250km and adding a further 450km.

The extent of the movement was worked out by researchers from Victoria University and GNS Science, with the findings published in the American Geophysical Union journal G-Cubed.


Dr Simon Lamb.
Dr Simon Lamb.

“I don't think anybody in their wildest dreams would have thought that displacements on the fault could be so large, and also change direction so dramatically through time,” Associate Professor Dr Simon Lamb, from Victoria's School of Geography, Environment and Earth Sciences, said.

The researchers made the discovery by looking at geological maps together with studies of the direction of magnetisation in the rocks.

The finding underscored the fact the Alpine Fault was the big seismic hazard in the South Island and had been for a “very, very long time”, Lamb said.

Other faults in central and southern parts of the South Island had played only a small role in the movement of the tectonic plates.


GNS Science earthquake geologist Robert Langridge studying layers in the trench across the Alpine Fault at Springs Junction. New research has found that the fault line may be the world's fastest-moving, having shifted around 700km in 25 million years. — Photo: Joanne Carroll/Fairfax NZ.
GNS Science earthquake geologist Robert Langridge studying layers in the trench across
the Alpine Fault at Springs Junction. New research has found that the fault line may be
the world's fastest-moving, having shifted around 700km in 25 million years.
 — Photo: Joanne Carroll/Fairfax NZ.


The next largest known fault displacement on land was on the Altyn Tagh Fault in Tibet, with a total movement of about 475km.

The new theory about the Alpine Fault was a major shift in thinking and the researchers had needed to provide convincing arguments to get it published.

The idea occurred to him only about six months ago, Lamb said. “I was calculating the motion of the tectonic plates through New Zealand and realised they were so much bigger than the movement everyone was saying had taken place on the Alpine Fault.”

His advantage was that coming from the UK he wasn't wedded to a particular way of thinking about it.


The findings may have implications for why the Alpine Fault is so prone to earthquakes. — Photo: GNS Science.
The findings may have implications for why the Alpine Fault is so prone to earthquakes.
 — Photo: GNS Science.


“We put together this team of people who came at it from lots of different directions to make sure this was right, that we hadn't made some terrible mistake and missed something.”

The idea was exciting but it was followed by a large amount of work. “You spend a lot of time checking. You have to go through an enormous amount of information to look at what other people have discovered. You do a lot of testing. In you mind you play devil's advocate,” Lamb said.

“It will be interesting to see what the reception is.”

The Alpine Fault started as part of the break-up of the supercontinent Gondwana, with New Zealand starting to drift away from Antarctica about 80 million years ago.


GNS Science earthquake geologists studying layers in the trench across the Alpine Fault at Springs Junction. — Photo: GNS Science.
GNS Science earthquake geologists studying layers in the trench across the Alpine Fault
at Springs Junction. — Photo: GNS Science.


That resulted in about 250km of movement along the Alpine Fault but in the opposite direction to the way the fault is moving today. Then “nothing” happened for tens of millions of years, Lamb said.

About 25 million years ago a new plate boundary formed and the Pacific Plate and Australian Plate started moving relative to each other “in a big way”.

“That's the situation today. You have the Alpine Fault breaking up this fragment of continent that split away from Gondwana,” Lamb said.

It had been thought movement along the Alpine Fault was getting faster. “Basically what we showed was that from the moment the Alpine Fault started to move in the direction it's moving today it more or less moved at the same rate.” That was an average speed of about 3cm a year.


__________________________________________________________________________

Read more on this topic:

 • Alpine Fault spreads across South Island, researchers say

 • When, not if: Alpine fault could cause 8 metres of movement

 • Scientists digging into new part of South Island's Alpine Fault


http://www.stuff.co.nz/science/77647999
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