Earthquake New Zealand

[David Lyttle]

Have talked to a friend in Rangiora north and east of of the epicentre who is OK - he did not lose services at all even though Kaiapoi not far away but nearer the coast was hammered. Soft sediments tend to liquefy during and earthquake with devastating consequences to any structure built on them. People were talking about water disappearing from ponds, appearing elsewhere and " mud volcanoes ". Brick masonry construction has no strength in an earthquake and these buildings suffered as well. Timber-framed houses perform pretty well as do modern engineered buildings.

The fault that ruptured causing the quake was completely unknown unlike many of the major faults in New Zealand (eg the Alpine fault) and in this respect a quake so close to Christchurch was unexpected. Wellington is built on a major fault line. However no place in New Zealand is totally safe from earthquakes.

I slept through the entire thing though many of my neighbours were woken by it.  However this evening we lost power for several hours due to strong north westerly winds. I also lost some trees in my garden. In this respect we have got off very lightly compared to our friends in Christchurch who will be dealing with the same storm.

[Luc Gilgemyn]

So glad to hear that at least all "our" NZLders are ok !!!   

[Lvandelft]

So glad to hear that at least all "our" NZLders are ok !!!   

So am I !! 

[Ragged Robin]

Looking at the photos it's hard to believe tha relatively few people were badly hurt and no one died.  Thank goodness that it struck in the early hours of the morning and so people were at home in bed and not in the street or office blocks.

Thinking of those Forumists and others whose homes were devastated and hoping all will be repaired without delay.

[Lesley Cox]

I had an email from Edna Parkyn who posts in the Aroid thread sometimes. Although she and her family are fine, their house contents are badly damaged, contents of the pantry smashed and broken, ornaments smashed, furniture broken etc. They have a water tank as well as town supply so are OK for that I think, and - having her priorities right - she says her troughs, pots and plants she will have on the weekend of 18th/19th at NZAGS Spring Show, are all fine too, including little bulbs.

There are still many broken water and sewer pipes being discovered so there's a lot to be done yet and still having aftershocks. Apparently the winds they were expecting were not so bad as predicted fortunately. Like David, we here have lost a few trees, eucalypts mainly and branches from the pines. Our temp today will be a max of 11C whereas it's set to be 21C in Christchurch, just 200 miles up the coast.

[David Lyttle]

Caught up with Stuart Murray this morning. Stuart lives at Kaiapoi which was one of the worst affected areas. Stuart is fine and has not suffered significant damage apart from losing some of his clay pots. He says the NZAGS  spring show will be going ahead.

[David Lyttle]

Here is a link to Geonet showing the fault an aerial photos of the fault trace. You can see the offset by the displacement of the irrigation ditches and shelter belts. 

http://www.geonet.org.nz/news/article-sep-4-2010-christchurch-earthquake.html

[fermi de Sousa]

Glad to know you guys are okay over there!
We're having floods in Central Victoria at the moment    - the locusts are due next month!
I guess we are "living in interesting times'!
cheers
fermi

[kiwi]

Family all fit and healthy, property a bit smashed around. A totally surreal experience.
The community has really come together and supported each other. No drainage or sewage here for at least one month! It's going to be a testing time. On the bright side some beautiful flowers came out today to lift the spirits like this Magnolia "Black Tulip", Narcissus "Rapture" and Erythronium "white beauty"
Life goes on!

[DaveM]

Wow, that Magnolia is a stunning colour. It appears that some semblance of 'normality' is creeping in with the go-ahead for the NZAGS spring show    Good luck and enjoy the occasion.

Back to the old days of the 'earth closet', I suppose (Not that I'm old enough to have had personal experience though....). Yes, it would perhaps make one appreciate the accepted niceties of modern living. We perhaps sometimes take such things for granted and that many people in the world do not have such facilities as potable water supplies and flushing toilets.

David, many thanks for the link to the geonet site. Amazing pictures of the surface ruptures along this fault trace. Such pristine features usually deteriorate rapidly and are rarely recorded so well. In this case it's as though the fault had 'read all the text-books' ... all the features present that theory would predict.  

PS some of my colleagues were asking what the tall narrow trees are that form the shelter belts in some of these photos?

[Lesley Cox]

Welcome, welcome, welcome Doug. So pleased you are all OK as we'd heard some mixed tales. I hope things can be sorted for you and your family ASAP. Just for once the Govt seems to be willing to dive in and help and there is apparently no shortage of money. As much as is needed will be made available.

It says a lot about the gardener's spirit that you have taken the time to make pictures of what is in the garden while surrounded by devastation. I wish you and all Christchurch gardeners, very well.

[Lesley Cox]

Dave, Canterbury's shelter belts are usually of Lombardy poplar or Pinus radiata or Cupressus macrocarpa. Canterbury has terrible nor'west winds though the year really but especially so at the spring and autumn equinoxes and without the shelter belts, there would be no soil at all left on the Canterbury Plains. Years ago I was driving to Lyttleton to meet the ferry that my soon-to-be-husband was returning on from Malaysia via his army camp in the North Island. It was about 4 in the morning I think, and dark. Suddenly a great cloud of silt and dust hit me and totally killed my car lights. I lost control of the car and ended up, still upright, in a paddock on the other side of the road and facing back the way I had come. A paddock on the western side of the road had been newly ploughed and disced and literally, the whole surface was blown off it. I still look at that paddock every time I pass it and think how lucky I was that it was early morning and almost no traffic on what is the main No1 highway up and down the whole country.

[David Lyttle]

David, many thanks for the link to the geonet site. Amazing pictures of the surface ruptures along this fault trace. Such pristine features usually deteriorate rapidly and are rarely recorded so well. In this case it's as though the fault had 'read all the text-books' ... all the features present that theory would predict.  

PS some of my colleagues were asking what the tall narrow trees are that form the shelter belts in some of these photos?

Dave,

Several of my geologist friends are up in Canterbury at the moment looking at the fault trace. Doubtless they are having a very interesting time as the fault that moved was completely unknown before it ruptured on Saturday morning. A geologist interviewed on the radio earlier this morning gave the following explanation; In effect New Zealand sits astride the Australasian and Pacific plates which move relative to each other. The strains set up by this motion are relieved by movements along the major faults (eg the Alpine Fault) but additional stresses can be set up at locations more distant to the major faults delineating the plate boundaries. Ruptures can occur at these locations as happened on Saturday morning.

The Geonet site shows maps of shallow and deep earthquakes recorded in New Zealand over the last 10 years. The deep earthquakes tend to be associated with the plate boundary whereas the shallow earthquakes are more widely dispersed. There is large region of the alpine fault in the middle of the South Island that has shown very little deep earthquake activity over the past 10 years. This would imply that this section of the Alpine Fault is locked at present. Because of this stresses might accumulate in the rocks further east which could eventually rupture as occurred on Saturday.

Judging by the shadows the shelter belts  in the photos are poplars.

Doug,

Good to see that you are back on line. Judging by the photos you posted you might have a few problems to deal with. All the best for the upcoming weeks.

[Lesley Cox]

I heard on the radio today that some farms have cracks a metre wide and several metres deep and that boundry fences and buildings have moved up to 4 metres from their original positions.

[annew]

That must pose interesting legal questions as to who owns what