Perched on the border of two continental plates, New Zealand's position in the Pacific Ring of Fire is precisely what gives the country much of its astonishing natural beauty. Its mountains, volcanoes and geothermal springs are all the product of intense tectonic activity. But geological beauty can be a double-edged sword.
Technically any new structure built in New Zealand has to be able to withstand intense quakes but footage has shown that, although older buildings in Christchurch seem to have been hit the hardest, plenty of newer ones that should have been able to survive a 6.3 quake have also collapsed.
Six months before the September earthquake – a less destructive but more powerful quake measuring 7.1 on the Richter scale – Christchurch's city authorities warned that there were as many as 7,658 earthquake-prone buildings that would have difficulty withstanding the kind of serious tremors that have now hit the city twice in the past five months.
At the time the council was toying with a highly unpopular proposal in which landlords would have to ensure that all older buildings were made fully earthquake resistant within 30 years or risk them being closed down. Heritage groups and the local chamber of commerce balked, warning that compulsory upgrades might cost the city as much as NZ$500m (£230m), a sum that now looks a pittance compared to the clean-up costs that the country is now facing. The rebuilding estimate for September's earthquake alone was already priced at $4bn, and yesterday's quake was far more destructive.
Professor Colin Taylor, an expert in earthquake engineering at Bristol University, says new buildings are now designed to "fail in a controlled way". But even those built as recently as 30 years ago would have struggled to stay upright.
"From the pictures I've seen, the majority of the buildings that have been damaged date from the 1970s and 1980s," he said. "This was a time when earthquake design was still very primitive. The more modern buildings would have performed much better. A lot of damage seems to have been caused from facades that have fallen from buildings. This is typical of older buildings."
There are fears that the September quake would also have "softened up" some buildings, making them even more vulnerable during subsequent quakes.