Christchurch residents have been living on their nerves for more than 12 months amid constant aftershocks, afraid that next tremor could be another "big one", repeating the disaster that ripped their lives apart a year ago.

"The hand of God comes down and gives us another smack," said writer Jane Bowron, who has chronicled the trials endured by New Zealand's second city in her book "Old Bucky and Me".

"When we get another big aftershock it takes us back to ground zero. It's groundhog day."

The South Island city has endured some 10,000 tremors since the seismic seizures began in September 2010, the most devastating a 6.3-magnitude quake on February 22 last year that killed 185 people and levelled much of the city centre.

Further major tremors rattled the city in June and December last year.

Firefighter Jim Ryburn said that unlike most disasters, where people can pick up the pieces and rebuild their lives, the ongoing aftershocks meant there was a constant feeling of danger and a sense of uncertainty about the future.

"December hit people really hard," he said, referring to a swarm of aftershocks that rocked the city on December 23, sending terrified Christmas shoppers fleeing from stores.

"We hadn't had anything major for a while, people were relaxing, looking forward to some time off. People were thinking 'yeah, I'm getting over it' and it physically messed with people. People were tired all of a sudden."

Residents say the mind freezes when the earth begins shuddering with jackhammer intensity, then roads become choked with traffic and telecommunications go down as people desperately try to check on loved ones.

It's an ordeal most would count themselves unfortunate to experience once, let alone four times in 18 months.

The overwhelming feeling in the city is one of earthquake weariness, but seismologists warn aftershocks could continue for years as the ground around a previously unknown fault that shifted in September 2010 continues to settle.

Some have fled. Official estimates say Christchurch's population of around 350,000 decreased by 10,600 in the four months after the February quake, although Bowron says the figure is outdated and many more have now left.

Others have adapted as best they can to what Christchurch calls "the new normal", where the threat of a major earthquake is ever present.

Bowron says she no longer feels comfortable walking under verandahs and would not contemplate using a multi-storey car park after seeing the tragic consequences of the February quake.

Everyday activities in the city such as gardening or going for a swim are no longer an option -- the local pool is "munted", in the local lexicon, while liquefaction -- quake-produced quicksand -- has put paid to tending flower beds.

With the downtown "red zone" area still fenced off because it is too dangerous to enter, locals have struggled to come to terms with the scale of the destruction.

Aviation company Helipro runs chopper flights over central Christchurch, with some of the proceeds going to an injured earthquake victim, and says more than 90 percent of customers are residents wanting a first-hand view of their stricken city.

Feelings are mixed about the first anniversary of the February 22 earthquake.

Bowron admits a "totally unscientific" fear another quake will hit, but remembers fondly the dignified initial memorial in the city's main park in the wake of February's disaster that brought the community together.

Ryburn, a firefighter for 32 years who worked during the quakes and has heard some "heavy stories" since being seconded as a welfare officer post-February, was uncertain whether he would take part, torn between a desire to honour the dead and a need to move on.

Some of his colleagues have left town for the anniversary.

Bowron says Christchurch, where entire suburbs have been condemned, now resembles a frontier town and is in the process of reinventing itself.

Once regarded as "a little slice of England" in New Zealand, it is aggressively recruiting internationally the thousands of skilled workers who will be needed in the NZ$30 billion ($24.4 billion) effort to rebuild the city.

Bowron said the injection of youth from countries such as Ireland had the potential to reinvigorate Christchurch and change the nature of the city from its fusty English roots.