'Creeping quakes' rumble New Zealand: researchers

May 23, 2012
File photo shows snow capped mountains near Hanmer Springs on New Zealand's South Island. Researchers have discovered New Zealand's earthquake-prone landscape is even more unstable than previously thought, recording deep tremors lasting up to 30 minutes on its biggest fault line.

Researchers have discovered New Zealand's earthquake-prone landscape is even more unstable than previously thought, recording deep tremors lasting up to 30 minutes on its biggest fault line.

Scientists measured the so-called "creeping earthquakes" when they investigated a puzzling lack of major seismic jolts along a section of the Alpine Fault, which runs the length of the South Island.

The quakes, which caused no surface damage, occurred 20-45 kilometres (12-28 miles) beneath the Earth's crust and continued for as long as half an hour, much longer than ordinary earthquakes.

In contrast, the 6.3-magnitude that killed 185 people in the South island city of Christchurch in February last year lasted just 37 seconds and struck at a depth of about five kilometres.

The quakes could not be measured by regular devices and researchers from Wellington's Victoria University had to place sensors in boreholes 100 metres deep to pick them up.

File photo shows the damaged Christchurch Cathedral in the New Zealand South Island city of Christchurch in September 2011. The 6.3-magnitude quake that killed 185 people in Christchurch in February last year lasted just 37 seconds and struck at a depth of about 5 km.

Aaron Wech said the research showed the Alpine Fault, regarded as New Zealand's most hazardous, did not remain still between but was constantly shifting.

Wech said the implications for future earthquakes were unclear.

"It could be that constant tremor builds up stress and may trigger a major fault movement (earthquake) or, alternatively, the activity may decrease the likelihood of a major quake by acting as a release valve for stress," he said.

"What's important is that we find out more about these tremor events, such as where they happen and how often, so we can better predict the hazard the Alpine Fault poses."

The research was published this week in the US journal .

The government's GNS Science agency estimates the Alpine Fault has generated four quakes of magnitude 8.0 or higher in the past 900 years, most recently in the early 1700s, and another is overdue.

It says there is a high probability one will occur in the next 40 years, producing "one of the biggest earthquakes since European settlement of New Zealand (which) will have a major impact on the lives of many people".

The Christchurch earthquake was not caused by the Alpine Fault but a previously unknown , part of a network of seismic fractures criss-crossing New Zealand, which lies on the junction of two tectonic plates.

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User comments : 7

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1 / 5 (2) May 23, 2012
It is not so surprising all the earthquakes. The earth is moving. But New Zealand is so beautiful that I feel the sadness for the people who live there. Subduction zone is very close to North island and that could be partial cause of Alpine Fault?


1 / 5 (2) May 23, 2012
One wonders if/when NZ will split and half of it drops off into the sea. In time the whole of NZ may be subducted and be recycled.
1.7 / 5 (6) May 23, 2012
I geuss god doesnt like christians much, does he?
Lex Talonis
1 / 5 (2) May 23, 2012
The god that the jews invented to justify their genocide of the middle east, doesn't like them much either.

But back to the earthquake issue.... I always thought that buildings that you can jump out of without getting hurt, are the only ones that ought to be built.

First storey limits, with thick grass to land on.....

Fire, earthquake etc... No problemo.
5 / 5 (2) May 24, 2012
I am a new zealander and the first thing I thought when I saw this picture was "oh ffs, why did they have to put sheep in that picture".
1 / 5 (1) May 25, 2012
Hmmm... The earth's belly is rumbling. Think about it.
Warm (hot to us) semi-viscous rock moves more slowly.
not rated yet May 27, 2012
Argiod, the Alpine Fault is a right-lateral strike-slip fault, not a subduction fault. So your prediction is unlikely to eventuate.

OverweightAmerican, first of all one wonders about your username given this revelation of your place of residence. Secondly, I don't think a location could be found in New Zealand in which no sheep were in view just kidding.

Oh, and everyone...arguing about religion? Why bother? And what is the relevance here? I mean really, grow up. What are you doing with your lives, seriously.

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