ARTICLE

New Zealand Earthquake Damages are Minimal Due to Good Building Codes

Compiled by Nick Hill, Chief Executive, Building Officials Institute of New Zealand from various newspaper acounts and the book, Quake: The Big Canterbury Earthquake Of 2010

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Devastation of homes after Katrina
Home damaged during the Canterbury Earthquake in September.

At 4:35am on Saturday, Sept. 4, 2010, the Garden City of Christchurch on the east coast of New Zealand’s South Island was vigorously shaken awake by a 7.1 magnitude earthquake.

Unprepared for Mother Nature’s fury, the slumber of those asleep came to a terrifying end, as the huge destructive quake began shaking the Garden City and surrounding districts, causing unimaginable damage to buildings and land. New Zealand’s Prime Minister, John Key, was later to describe the earthquake and subsequent damage as New Zealand’s worst natural disaster.

Remarkably, there were no deaths; however, had the earthquake hit two to three hours earlier when the streets, cafes and businesses were buzzing with people, authorities predicted the death toll would have been well into the hundreds, if not more.

Authorities also believed the New Zealand Building Standards and Codes, implemented after the devastating Napier earthquake in 1931, and regularly amended, played a significant part in the building stock not becoming the death traps they potentially could have. Many of the damaged buildings, their brick and masonry structures cascading down onto the roads and footpaths as the unreinforced walls crumbled under violent shaking, were built before World War II.

Devastation of homes after Katrina
Bathroom floor damaged during the Canterbury Earthquake in September.

People were thrown from their beds, walls crashed onto cars, and thousands of chimneys crashed through roofs in the tremors that rippled and buckled the ground from Kaiapoi just north of Christchurch to Darfield in the west and Temuka in the south.

In seconds, it tore up streets, cracked concrete slab foundations of many houses, cracked solid walls and rendered many homes uninhabitable as power, water and sewage services were lost.

Many Christchurch and surrounding town dwellings were built on soft ground, which shook and rocked causing liquid to rise into hundreds of fountain like gushes—“liquefaction” being the new word in everyone’s vocabulary.

At the time of publication the cost of damages is estimated to be in excess of NZ $6 billion (Approximately $4.63 billion U.S.)

Click here to see Canterbury Earthquake Claims Information as of November 2..

A Personal Account of the Sept. 5, 2010 Christchurch Earthquake

By Stewart Geddes, Building Control Team Leader, Central Otago District Council

This is an account of my personal experience as a Building Control Officer deployed to help our counterparts in Christchurch after the earthquake.

At 11:45 a.m. Wednesday, Sept. 8, a nationwide call went out from the Ministry of Civil Defence and Emergency Management in Christchurch for 60 building inspectors to help assess homes damaged by the earthquake.

The Central Otago District Council sent three inspectors – Murray McCutcheon, John Watson and me.

By 7 a.m. the next morning, 60 building inspectors were on the ground in Christchurch ready to go, with another 20 on standby. They came from everywhere – from Invercargill through to Auckland.  To think that within 24 hours they were on the ground ready to go was incredible.

We assembled at 7:15 p.m. at Christchurch Art Gallery for our first briefing of the day. We then deployed by bus to Linwood Service Centre, which became the working base for the building inspectors.

Teams of Three
The second briefing of the day took place. Teams of three were set up consisting of one building inspector, one health inspector or plumbing inspector, and one welfare officer, who was either someone from the Red Cross or from a group of volunteers.

Fifty-seven of these teams were then assigned an area in which they were to check out the safety of the buildings and the people living in them. Our teams were involved in checking residential properties only.

Building inspectors checked the structure to see whether it was safe for people to remain in the building. Health inspectors checked on sanitary conditions and on whether there was water or sewerage available. Even if they didn’t have water or sewerage, people had the option to stay in their homes, and that was what most people wanted to do. There were “port-a-loos” on the streets and water available. The welfare officers asked people questions like, “How do you feel?” “Do you have food and money available?” and other general well being questions.

All three inspectors’ notes for an individual property were then filed together, picked up throughout the day by couriers, taken back to Linwood and entered into a database.

People Needed to Talk
We only had 10 minutes to assess each building, so there was no spare time to stop and chat.

You can imagine this was hard when you were dealing some people that wanted, perhaps needed, to chat. Sometimes we just needed to stop and spend extra time, as these people needed reassurance about their safety. We did have social workers on call that we could bring in for extreme trauma situations.

Once we completed the assessment, the building received a green sticker if it was fit for occupancy. It received a yellow sticker if people had to move out of certain parts but could remain in the rest, e.g., if a brick chimney was cracked and could topple over and down through the ceiling, the yellow sticker identified the rooms around the area as ones not to be used. We gave a red sticker if there was to be no entry whatsoever due to safety concerns over the structure. We gave this to buildings that had huge structural damage and would probably be demolished.

Building inspectors had engineers on call that they could bring in if they needed a second opinion on a building or if the needed assessment was outside their scope of expertise.

Characteristics of Homes that Suffered Less Damage
The dwellings we inspected ranged from early-1960s State houses to current era housing. The standards have not changed much and are in line with today’s NZS 3604. Timber-framed buildings very similar to NZS 1900:1964 were used back in the 1960s.

The majority of State houses on piles we inspected were fine from the floor joists up, apart from minor jamming of opening windows and doors. But the perimeter foundations had cracked right through every three to four meters (10 to 13 feet) and the reinforcing rods held them in place. The other issue with these houses was the unreinforced brick free-standing chimneys that tended to break off at roof level and either fall down through the ceiling or down the roof and onto the ground.

The houses we inspected on solid concrete foundations and slabs built to NZS 3604 fared well because they were a floating foundation, and although they stayed in one piece the levels altered with some ground levels lowered and some risen. It was common for a house to have 400 millimeters (about 15 ¾ inches) of cross fall from one end to the other but no structural damage to the house. This was due to the liquefaction coming up through the ground and altering ground levels.

In the extreme case where a fault line went right through the middle of a house, forces proved too much and the damage was beyond repair. To have only 12 houses in the residential sector that needed to be demolished is amazing. This has to be due to the high standard of building in New Zealand and the fact we have good building code and a documented standard based on the Building Act, the New Zealand Building Code, and associated New Zealand Standards such as 3604 for Timber Framed Buildings and 4229 for Concrete Masonry Buildings Not Requiring Specific Engineering Design. These Standards are designed for New Zealand conditions and draw on international and local best practice.

Some of the commercial unreinforced brick buildings in Christchurch had already been upgraded to comply with Christchurch’s Earthquake Prone Building policy. These buildings had been strengthened to 33 percent of today’s Standard AS/NZ 1170:2002 and had significantly less damage than the buildings with no strengthening. It is interesting that the Christchurch City Council has changed the 33 percent in this policy since the earthquake, increasing it to 67 percent of today’s Standard AS/NZ 1170:2002. This was introduced to minimize further future damage.

The Emotional Toll
Concerning the emotional side of the earthquake, I personally found the first contact with these homeowners very humbling, as we were the first official people to talk to them. This was a huge relief to them, with some people just breaking down in tears once they describe their experiences. You were delving right into their personal lives, walking right through their homes looking through all the rooms checking for damage.

To listen to people tell us they had no food and no money was extremely sad and emotionally draining. For people to have the courage to tell a complete stranger this, sometimes with no emotion, was amazing. However, 99 percent of people were pleased to see us.

After three days of checking out buildings, we scaled back the operation, since we had completed assessment of the worst affected areas.

The randomness of the devastation was amazing, with perhaps only three houses on a street affected, some so badly they would have to be demolished.

Then there was the looting of houses by thieves, some with orange fluorescent jackets posing as building inspectors. Police took a very hard line on this type of activity. Once a burglar sees a red sticker on a house, they know it is unoccupied, so it’s an easy target.

Valuable Lessons

No amount of planning can prepare you for a disaster of this magnitude. The whole country will benefit from this disaster once a debriefing is held and lessons are gleaned and learned.

Again, I must congratulate all Building Control Officers across New Zealand for helping Christchurch City in their hour of need and continuing to help with ongoing support.

We have learned some invaluable lessons that we can put to good use at our own Council, and am sure the whole country will learn how to be better prepared for a huge disaster.

As always, your articles ideas and submissions are welcome. Send them to foliver@iccsafe.org along with a daytime phone number at which to contact you with questions.