Christchurch quake: Stress leaving toughest in tears

Geotechnical engineer Jan Kupec has been checking demolition sites on the cliffs to ensure they are safe for work to resume. Photo / Mark Mitchell

Thousands of tonnes of rocks and rubble fell from cliffs not far from houses in Sumner and Redcliffs in the 5.7 aftershock on Sunday but one expert said the most significant damage would be psychological.

"I've had some really strong people on the phone to me in tears. Good resilient people," said Brenden Winder, of Land Information New Zealand.

"It is more the psychological and social [damage] than damage to houses and infrastructure. This has literally smacked people in the face."

Mr Winder is group manager of property owned by the Crown on the Port Hills, which includes badly damaged residential properties bought from residents or insurance companies for safe demolition.

"If it was just one thing it wouldn't be a big deal. You get liquefaction, then your house gets beaten up, then you're in a dispute with your insurers, then your kids can't go to school.

"It keeps coming to the point it just overflows."

Mr Winder and geotechnical engineer Jan Kupec have been checking demolition sites on the cliffs to ensure they are safe for work to resume. Both men said it was fortunate that the earthquake happened on a Sunday, the only day the clifftop demolition sites are not worked on.

Mr Kupec said it was a continuation of earthquakes from the Banks Peninsula volcanic system which produced "short, sharp, violent earthquakes like Sunday".

"We are looking at smaller scales of damage but still significant. Hundreds of cubic metres has fallen off Richmond Hill for example, dozens of cubic metres at Red Cliffs and probably thousands of cubic metres along Whitewash Head and Godley Head.

"Our job now is to assess the damage, prioritise the sites that can be [restarted]. We go back to square one and ask the question where it is appropriate to continue the work."