Our craggy, energetic land moves to its own rhythms regardless of who lives on top of it. This is why we need to prepare for the worst, knowing that such readiness will at least take some sting out of what is inevitable.
Three significant earthquakes in the past 15 years — two damaging and of large magnitude, one smaller but highly devastating — have determined the way many people think about what we can do to ensure our older buildings are safe, both to occupy and to walk past.
Most deaths and injuries in a major earthquake are caused by collapsing buildings and falling masonry.
In the destructive magnitude 6.2 February 2011 Christchurch earthquake, 185 people were killed — 115 and 18 respectively in the collapses of the Canterbury Television and Pyne Gould Corporation buildings. Many other victims were hit or trapped by debris, or were in vehicles crushed by masonry.
The magnitude 7.8 Kaikōura earthquake in November 2016 was a huge event. Two people died in their home at Mt Lyford in North Canterbury and some Wellington buildings had extensive damage from long-period shaking, requiring their demolition.
Little wonder then that our national sensitivities have been heightened to what could occur when the next large quake strikes. In the wake of these tragedies, and the Canterbury Earthquakes Royal Commission of Inquiry, major adjustments were made to the country’s earthquake-prone building regulations which, on reflection, were perhaps overly zealous.
On Monday, the government announced a raft of changes to that system, which had placed a massive financial burden on property owners and councils and on small towns throughout New Zealand over assessing and managing seismic risk, even in regions with a low probability, based on historic records, of a damaging event.
Buildings in Northland, Auckland and the Chatham Islands will no longer be in the quake-prone catalogue, due to the low risk of a damaging earthquake there — however, volcanoes and earthquakes go hand in hand). Also, small buildings in towns with fewer than 10,000 residents will be exempt, once owners of buildings on the list have secured facades.
Of most interest, however, is the change in risk for coastal Otago and Dunedin from low to medium. This may not find favour with property owners and developers here, but it is a reflection of recent research on a number of active faults close to Dunedin, such as the Akatore and Titri faults, which could potentially generate quakes of around magnitude 7.0.
It is easy for residents in this region to become blase or be naive about earthquakes, given a quiet recent history. But the risk here encompasses far more than just the likelihood of major shaking from a probable magnitude 8.0 or higher Alpine Fault quake in the next few decades.
When it comes to mitigating risk of any kind, including natural hazards, there is always going to be a tradeoff between life and cost. Mr Penk, among others from the government, estimates the new system could save more than $8 billion, with several thousand buildings removed from the quake-prone buildings register.
Dunedin nurtures its heritage buildings and has built a formidable reputation and a tourism industry around them. There will naturally be anxieties about precisely what the changes might mean and about the increase in its seismic-risk profile.
Developers in the city will be watching closely and awaiting more details about how many more buildings may now be considered earthquake prone and how much it might cost to bring them up to standard.
There is a fine line to tread between over-reacting to the news and fearing its implications on Dunedin’s heritage, and being sensible and remembering the importance of doing what can be done to protect people.
The lessons from the dreadful Christchurch earthquake should never be allowed to fade.
