Building code saves NZ from serious destruction

Updated September 6, 2010 17:42:20

As we've heard in earlier reports, many New Zealanders are assessing the damage from the weekend's earthquake. Jeff Crosier, is a structural and earthquake engineer from consulting firm Miyamoto International. While the New Zealand earthquake was larger than the one which devastated Haiti earlier this year, killing 200 thousand people, Mr Crosier says it is surprising how little damage has been caused in Christchurch.

Presenter: Stephanie March
Speaker: Jeff Crosier, a structural and earthquake engineer from Miyamoto International

CROSIER: Well the quake itself was actually was a pretty good size quake 7.2 magnitude is a relatively large earthquake. Now that said, we have extensive damage to buildings that we would normally expect to see in a less developed area. The engineering here seems to be very good. The primary damage we've seen to buildings is chimney collapse reinforced walls collapsed, as of yet I have not seen any advanced damage to any highly engineered structures. There has been a lot of disruption of water and utilities and non-structural damage, so far, but not as extensive as you would anticipate.

MARCH: Would you say that New Zealand's building codes could be to thank for the lack of serious damage to as you say large structures?

CROSIER: Oh certainly, the building codes is advanced here as anywhere in the world as is the structural engineering profession, so I would think a lot of credit would have to go to both of those things.

The other thing that I have seen here that has been quite good is the emergency response. It seems like the teams are very well trained. I have been staying in the city centre and in Christchurch and that area has been cordoned off immediately and I think arrived within 30 hours of the earthquake and all the critical areas have been roped off for hazard damage and they are not accessible to the public, and there are already teams of urban search and rescue going through and assessing all the buildings and marking the buildings that are safe and not safe. So the response is very rapid and it has been very aggressive, so that is quite impressive.

MARCH: There's obviously been a lot of damage done to infrastructure and things like sewerage and water supplies. We've seen images of cracked roads, sewerage and water spewing out of them. Is that quite a serious problem there in Christchurch now?

CROSIER: Well, it is actually. I think in some of the areas there is a lot of liquefaction areas, there has been a lot of ground subsidence and some lateral spreading and of course the earthquake fault has shifted the ground in some areas along the fault that has led to some fracture of water mains and sewer lines and elements to that affect. But that generally has it really has a bad affect on the population and overall because we don't have water supply in many of these areas. But since power has been restored, in many of the areas of water and sewers are still lacking in some areas.

MARCH: In terms of rebuilding and repairing a lot of the infrastructure damage, what do you think needs to be kept in mind?

CROSIER: Well, I think more understanding of the liquefaction potential of the areas, especially close to the sea. Liquid faction is where soil typically very sandy soil has a high water table and it shook violently like by an event such as an earthquake, it can lose its ability to support load and it really just liquefies and that is what we've seen in the New Brighton area, pretty extensively where the sand will just boil up out of the ground and it will settle dramatically and that causes a very, very bad effect to buildings that may be sitting on that or to roads that cross it. Liquid faction has been a phenomenon. I know in the US it has been addressed only very vigorously in the last 15 to 20 years and I suspect that is the case throughout the world. So better understanding of that will led to better judgement about placing critical elements in the ground such as lifelines and things lines and sewer lines and that sort of thing.

MARCH: And just from your observations on the ground in Christchurch. Has rebuilding begun or are people still trying to come to terms with what's happened and just clean up and emergency services make sure that everyone is okay?

CROSIER: Yeah, I think it is still in the response mode. What I have seen so far is that there they have done a lot of cleanup. They have cordoned off areas and they are in the process of removing their debris right now which is actually very rapid. I kind of think there is no human recovery process there. Fortunately, none was killed and the injuries were very minor for the size of an earthquake, so they are rapidly doing the cleanup and I am sure the rebuilding will start rather quickly.