June 4, 2011

Fault structures revealed in Christchurch

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So we have a few areas with fault lines.... not unexpected but interesting... and there is another good picture of the area and the aftershocks on that site too. http://www.gns.cri.nz/Home/News-and-Events/Media-Releases/Fault-structures-revealed

The real question for us is whether the two current active faults will join up - seen in the dark blue aftershock dots on this faults map - with the red fault lines either end. I don't know enough about it to comment, but we will all be interested in the opinions of the experts.

We were told last night that testing below a building near the river had showed they would have to go down to 30m to find solid rock for new foundations - wondering if a rebuild will be possible, or advisable?

Apparently, this is not dampening our optimism? Yeah right..
http://www.stuff.co.nz/the-press/news/5099592/New-faults-fail-to-dull-optimism
You can read more here.... and this is an extract...

Three confirmed new faults and two other areas of likely active faults have been identified near Christchurch by scientists examining seismic hazards around the city.

Extensive surveying over the past two months has uncovered a 25-kilometre-long fault under the sea off Kaiapoi. Two faults run almost directly below central Christchurch and two patches containing possible small faults – one off the Brighton coast and the second just north of Port Levy and Pigeon Bay.

But the outlook may not be as grim as it sounds. Scientists delivered a largely optimistic message for the people of Canterbury at a briefing yesterday. Despite their findings they say: The tsunami risk from the large offshore fault is believed to be very low because it is unlikely to generate a quake higher than magnitude 7.0. Also, its past movement has been mostly horizontal rather than vertical.

There is no sign that aftershocks are spreading offshore onto, or close to, it or other already recognised Pegasus Bay faults.

The offshore faults are very slow moving, among the slowest moving in the country.

The faults underneath Christchurch are not particularly large and appear to have very long intervals between rupturing.

However, they also say the findings released yesterday are preliminary and that more research is needed.

The most important missing piece of the puzzle are results from the underground surveying of what has become known as "the gap".

Survey lines in the aftershock-rich area between the eastern end of the Greendale Fault and the western tip of the Port Hills fault were completed only last Saturday.

Canterbury University geological sciences Professor Jarg Pettinga , who has directed the seismic surveying work, said the analysis was under way but it would take another four weeks or so before those findings could be released.

Earthquake Recovery Minister Gerry Brownlee said the media briefing was a chance to update the public on everything scientists had been able to deduce so far about the Canterbury quakes.

Findings from the intensive research programme would inform future building codes.

Posted via email from Four Paws and Whiskers

2 comments:

  1. mmm It keeps us alert Certainly we don't get to settle yet. Let's hope the new findings turn out well. It also indicates that rebuilding is going to be very complicated. Wonder how it develops further. Very interesting information. I put a link to it on my site. Take care

    ReplyDelete
  2. Hmmm. It sounds to me as if our ancestors had known then what we know now Christchurch would have been built elsewhere. Hindsight and all that.... But then who knows: we are notoriously fickle creatures.

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