Earthquake Damage in Christchurch

Christchurch is a city with a population of just under 400,000. We have just had an earthquake that was slightly stronger than the one that did so much harm in Haiti. The amazing thing is that no one was killed and only a few people were seriously injured. Our Prime Minister has called this a miracle. He probably does not have the same definition the word, as I do, but perhaps he was right.

Central Business District
The first European settlers came to Christichurch in 1850, so there are no building more than 150 years old. The worst damage is in the central business district. Modern high rise buildings seem to be okay, apart from cracks on the stairs and ceiling panels falling out. Modern engineering standards seem to have done their job.

The older part of the CBD was probably built around the beginning of last century. These building have brick walls and are two or three stories high. Many of the walls and frontal facades have collapsed into the streets, but most of the structures are still standing, so few of the floors actually collapsed.

This photo is an example. The top floor was a Thai restaurant and the ground floor was a jeweller shop. I presume most of these old buildings will have to be destroyed and rebuilt. The new building across the street seems to be okay.

At the moment the central business district is closed off to everyone except business owners, because there is fear that some of the buildings may collapse, if there is a serious after shock.

Several shopping centres in older suburbs are also two-story brick buildings. Their walls have collapsed in several places.

Many older churches built from brick have been severely damaged, but the more historic buildings that had earthquake strengthening are okay.

Housing
The damage to houses is severe in several suburbs. Most people in Christichurch live in detached houses. Some of the wealthier people live in two-story houses, but the vast majority live in single level houses. A few of the older two-story houses have been converted into several flats that are rented.

Houses in New Zealand are built with timber framing and clad with weather boards or bricks. When the cladding is brick, it is only used as a veneer, as the roof structures are supported by the timber framing. The result is that very few houses actually collapsed during the earthquake.

Older houses tended to be built on timber or concrete foundation posts. New houses are built on reinforced concrete slabs, often referred to as floating foundations.

The worst damage came from older style being shaken off their foundations. Others were damaged when brick chimneys fell through the roof of the house, collapsing into the rooms.

Liquefaction

This was not really in an ideal place for building a city. Some of the city is on an old flood plain and parts of it are very swampy. Not surprisingly, liquefaction has been a serious problem. This occurs when the shaking of the earthquake presses sandy soils closer together, squeezing water out. Water is pushed towards the surface and squirts out in a little fountain, bringing silt with it. This photo is in an example from a park, near where I live. It looks like a mini volcano. Others were much bigger.

Where modern houses have been damaged this is mainly due to liquefaction. This photo shows what is probably one of the worst hit streets. These houses are less than ten years old. The silt has been carted out from around them. Some had half a metre of silt that came out of the ground lying on their lawns. The houses foundations have collapsed and the wall are cracked, so they will probably have to be demolished.

Streets

The earthquake has really damaged the streets. These photos show damage to the streets about 300 metres from where I live. The cracks are much worse in other places.

The asphalt is cracked and water and silt has come up from below. I presume that the foundations of the surrounding houses will be severely damaged, despite being almost new.

Fear
The pervading emotion is fear. Fear and terror are everywhere.

My soul finds rest in God alone;
My salvation comes from him.
He alone is my rock and my salvation;
He is my fortress, I will never be shaken.
(Psalm 62:2)