Earthquake in Christchurch points to troubled months ahead

The city of Christchurch is still in shock after Tuesday’s devastating earthquake and resulting loss of life – on Friday, reports suggested 113 confirmed fatalities with around 200 missing. While the current focus is on the search and rescue effort, the disaster is eventually likely to lead to questions about the suitability of New Zealand’s earthquake code.

The devastation came six months after the earlier “Darfield” quake on September 4th 2010, which resulted in only one fatality and was  described at the time as a one in 16 000 year event.

The damage to the city’s building stock from the earlier event has been put at US$3bn, a figure likely to be dwarfed by the impact of the latest disaster.

Over 30 buildings have collapsed in the Central Business District and the entire CBD is closed to all except the rescue teams, who have had to contend with continuing aftershocks.

Peter Cunningham, formerly chief executive of the Construction Clients Group in the UK, is now a director of Constructing Excellence in New Zealand. He said that the natural disaster was the worst New Zealand had experienced since the Napier Earthquake of 1931, which killed 256 people, and  would probably prove to be the worst in its entire history.

In an email to CM, he said: “The people of NZ are in a state of shock and are now pulling together in support of Christchurch. This is a small country with a strong community spirit. It is a very sad time with many people upset.”

He added: “From a construction perspective, prior to this week’s 6.3 magnitude event the sector had been gearing itself up to continue the rebuild effort following the original 4th September quake.

“So, many companies were in the process of recruiting and building resource to meet the rebuild demand – what impact does this week’s quake have on those companies? Obviously this entire programme of work is now on hold as buildings are assessed or re-assessed.” 

However, an additional priority will be re-examining the country’s building codes. Since the  Napier earthquake, these have included earthquake protection measures, including seismic bracing and the insertion of seismic joints between buildings of different ages.

According to a recent article on the Darfield Quake in CM’s sister magazine iCon, historic buildings in Christchurch, including the city’s damaged cathedral, have also undergone strengthening works.

But Don Moller, an architect who formerly practised in New Zealand and is now retired and living in Australia, said that the evidence from TV coverage suggested there had been failings. 

“Some of the buildings shown collapsed on TV were built in the 1960’s and should have met the requirements of the NZ Earthquake Code and structural stipulations to cope with seismic loads from an earthquake.

“They obviously haven’t been able to meet the seismic loads from this earthquake. Columns have been sheered at beam junctions and RC slabs have broken up. It’s possible there was inadequate steel content [in the concrete].”