In 1996 a TV documentary warned about the dangers of an earthquake in Christchurch, many of its predictions has since been proved correct. At the time this video would have been dismissed as scaremongering. Please read this blog entry in conjunction with another we wrote in December 2010 headlined “Christchurch earthquakes warned about as far back as 1995”

A cut of the documentary, compiled by a YouTube contributor, shows that building and infrastructure problems were well known about and understood in 1996; as were the dangers from liquefaction in the  ground beneath the city. Even where earthquake prone buildings were identified, the requirement at the time was that they only had to be strengthened to a fraction of the standard. Come the Big One it may turn out to be a “waste of time.”

(For a post-quake TV3 follow-up on the video click here)

Some dialogue from the 1996 documentary:

…But Christchurch does have a fatal flaw:  sits on a soft, shaky sponge of riverstones and silt half a kilometre deep. In any decent quake the garden city will shake like a leaf.

And that’s not all, scientists have discovered many earthquake fault lines (Hope, Napier, Esk, Porter’s Pass-Amberly, Pegasus Bay) any of these could cause huge earthquakes but overshadowing all of these is an immense super fault further back within the Southern Alps. This alpine fault runs from Fiordland to the top of the South Island… (talk about the Alpine Fault and it triggering other faults)

John Christianson(Principal Engineer) Connell Wagner: “Liquefaction literally turns the soil to water and structures that used to be supported by the soil will sink, structure which are buried in the soil will float.”

When soils liquefy sewers and drains come apart, roads break up and buildings sink or tip over. Liquefaction will cause major damage here too and no-one knows if the water supply will stop or be polluted by a large quake.

Alan Watson, Unit Manager (Sewers) Christchurch City Council: “Christchurch has got quite a high susceptibility to liquefaction, especially in the eastern part of the city.”

And how many breaks will you expect?

John Lamb, Regional Controller, Civil Defence Canterbury: “Many, many, many breaks. It was suggested perhaps of the order of 65% of the pipes.”

Whilst new plastic pipes should cope with the shaking, half are old made of earthenware clay. These will pull apart and block up. Raw sewerage will spill onto properties and into streams,

John Lamb: We would be wanting to discharge in to both of the main rivers – The Heathcote and the Avon. It could be up to 2 years before people could use their toilets in the normal way and flush it.”

After the Hawke’s Bay earthquake, various changes were made to building standards

Brian Bluck, Manager Building Control (Technical) Christchurch City Council“…and then in 1991 they adopted the Building Act. And again instead of coming up with some modern technology and better wording – giving us something we could use – they go back to a standard which is not changed in 60 years. ‘Cause what’s in there is just a smokescreen for lawyers“

So what does Brian Bluck think of his own patch? cut to street scene of Mr Bluck looking at an old brick building

Mr Bluck: “Oh I can see little cracks over that window arch where the cracks coming down to the window. If you look over to those windows there all the mortars come out from between the bricks… Along the top there its not in a very good state. So, If we serve notice we can only ever get them to come up to half of 1965…its certainly making sure that those parapets won’t drop on you or I when we’re on the street but its not going to make sure you’ve got a building the day after the earthquake.”

All buildings must be strengthened to just one quarter of the strength of a modern building, that won’t help much in a big earthquake. There are hundreds of old buildings which haven’t been strengthened at all.

Mr Bluck:” But over the road we’ve got a building where they’ve started to do the strengthening. They’ve put some reinforced concrete frames in the bottom, the parapet has come off the top. They’re spending the money on structures whereas over behind us ‘we’ve’ put paint on the building, some lovely weeds growing the the parapet. All they’re doing is ruining the mortar and making sure that the bricks are just an amorphous collection of bricks.”

“David Sargeant, Chief Executive Officer -Insurance Council of NZ: “Most of the pre 1935 properties that haven’t been strengthened, uh..pose a major risk, uh..both for the tenants who are in them and the property owners. And the insurers essentially won’t touch them.

Mr Bluck: And this is where we come to what was the old D.I.C. building. Now there have been several alterations in the last few years (film of an old elegant building) and those green columns at the floor there are a lot more substantial than they were, and there’s a whole framing system…”

Today there’s a strong interest in restoring historic buildings. Are they a big risk?

Mr Bluck:”Well really, your heritage list, to be quite cruel, defines most of your earthquake prone buildings.”

When the Big One comes it may turn out to be a complete waste of time

Mr Bluck: Well every time we get an earthquake of course, it cracks a few more elements and makes the building less able to resist the next one…The day after the earthquake you may well have to demolish it because its dangerous.”

…But Christchurch has its success stories, saving a building’s character and making it safe – like the old Normal School (shot of school)

Professor Park, Engineering Dept – University of Canterbury: The University of Canterbury Library has been shown to be a typical building of the 1970s. The upgrade on it which is being considered now would be to put in more walls to make the structure symmetrical and also to prevent the likelihood of any column failure. Why? Well I believe as a building owner we have a moral responsibility, particularly in a library building for example which is occupied by hundreds and hundreds of people each day”

Why should you consider it morally and yet other people don’t?

Prof Park: “Well its a question of money I suppose”

Christchurch Women’s hospital has another building with a shaky future, research here turned up some alarming results

Ian McCahon, Geotechnic Engineer -Soils and Foundations ltd: The Christchurch Women’s site was by far, if I can use the word, “worst” amplification and they were recording something like almost twenty times the maximum degree of movement there than there were in the Port Hills.”

The figure is based on small earthquakes recorded in the nurses home basement. The impact of a big earthquake could be somewhat less because of the dampening effect of loose soil but the shaking will be at least 4 or 5 times greater than on hard rock

The results for the ground shaking – does that concern you?

Dr John Taber, Institute of Geophysics – Victoria University of Wgtn: “Wah because I think that they are very aware of it, uh in that sense I’m not concerned because they know the problem exists and they’re working on way to solve it.”

Ian McCahon: “Well its still of concern, its quite clear that the Christchurch Women’s site is, and the immediate area, is going to be susceptible to very pronounced shaking”

A number of things need to be wrong for a building to collapse: its age and design, the intensity and direction of the earthquake and the soil below. Soft soil can be bad but if the soil is also of the wrong depth its destroying effect can be far worse. Usually a building moves at a different speed to the ground it sits on but if the soils depth means more vibrate together he shaking can be incredible. This extreme shaking happens at the resonant frequency.

If the nurses home turned out to be at resonant frequency to the soil what could happen?

Dr  Taber: “Yeah I suppose if the frequency of the ground is the same as the frequency of the building and you have an earthquake at a good enough distance so that the soils really are amplifying then you are likely to get more damage”

Do you have a moral obligation here to warn?

Dr Taber: “Well I certainly, I wouldn’t uh, I-I wouldn’t hide information…”

What frequency does it reveal?

Ian McCahon: “So normally you’d be looking at perhaps a five or six storey building, its going to be subjected to very severe shaking.”

The DIC building in Lichfield Street was partially demolished, except for its façade,  in 2000.

Demolition of the old Christchurch Women’s hospital (built on Colombo Street in the 1950s) began in September 2008. Colombo Street was extensively damaged during the quake, a bus was crushed by falling debris.

Information about how the quake affected the University of Canterbury may be found on its Facebook page. Some of its buildings were damaged in the quake, a few were red-stickered (including the registry building and ball room of the UCSA building) and some classes are to be held in the new Tent Town in the car park.

Canterbury TV  and Pyne Gould Corporation buildings

The New Zealand Herald unearthed some Quotable Value reports for these two structures which said

“Christchurch earthquake: Collapsed buildings on soft soil – QV”

“…The property-hazard reports for both buildings, compiled from a variety of official sources, say they are on ground classified as “very soft soil”.

“In a strong close-by earthquake these materials could cause … a moderate increase in shaking for high-rise buildings.

“In a strong distant earthquake these materials are likely to cause a large increase in shaking.”

The reports also say the buildings are “in an area where the ground is classified as having a susceptibility to liquefaction that is very high”.

GeoNet project director Ken Gledhill said liquefaction probably occurred in central Christchurch as well as in the suburbs, but large buildings were expected to have substantial foundations to combat it…

…Buildings erected under modern building codes could survive without damage, and that was shown by the Inland Revenue Department building across the road from the CTV site.

“It is a normal glass building,” Mr Key said. “Not a pane of glass broken, it is in perfect condition.”

“read the full report on the Herald’s site

Comments left on YouTube for the 1996 doco video included the following:-

“When a few of the bad suburbs were being built, the council said no to building there because of the land. But the developers took them to court and won, now we are in this situation.”

“I find it interesting that the so-called success stories, were badly damaged in the September earthquake such as the Normal School.”

“when they talk about “there are hundreds of old buildings that haven’t been strengthened at all” I see that metal dome that came down in the february quake (at 4:10).”