Fifteen months of aftershocks have pushed them to breaking point. Now they've had enough.
"We don't know what to do, but we can't stay here," said Mr Yambasef.
"We were excited about a bigger house for our children, but now we want out. This really is the final straw."
Mr Yambasef was already shovelling mud from the first aftershock when the second one, of 6.0 magnitude, hit at 3.18pm.
"Everything was really rocking. It was a pretty violent shake, and now look at it. The liquefaction is just too much to deal with. The smell of sewage is awful. It reeks in the hall and bedroom. The walls are cracked."
The damage comes days after the family regained basic services for the first time since the February 22 quake that killed 182 people.
"The sewerage was off for seven months and only last week was it
officially fixed," Mr Yambasef said. "They took our portaloo away last Friday. It's unbelievable."
He said the family had to be close to autism centres for Dante.
"But we need to get out of here. It's no good for him, he can't play outside and that is good therapy for him. And his sister is terrified.
"This is where I was born and raised, but you have to do what is best for your family."
A few doors down, Judah Matenga, 43, was wading through the sludge in his front yard and coming to a similar conclusion.
His wife, Sarah, was at the Palms Shopping Centre in Shirley when yesterday's first shock hit.
"It was pandemonium," said the 36-year-old. "People were panicking, lots of ladies crying, the look of shock on people's faces ...
"We got out and rushed home to find our place covered in liquefaction - again."
The Matengas were badly hit by the tragic February 22 quake, but believe yesterday's tremors were more unforgiving.
"We got liquefaction badly in February but this is twice as bad," said Mrs Matenga. "The house had sunk 30cm, but God knows how far it's sunk now."
The family are just back from a holiday in Australia. Now they are planning to go there permanently.
"That's the plan, move to Oz," said Mr Matenga. "This is the last straw, really. Christmas still has to go ahead, but after that we'll be out of here."
Experts predict many others will join the Yambasefs and the Matengas.
The ANZ Bank was accused of pessimism after predicting the September 2010 quake would prompt 5 per cent of the city's people to leave.
Its chief economist, Cameron Bagrie, said yesterday that figure "seems too light" and the final tally could double.
Christchurch Mayor Bob Parker said the aftershocks inevitably delayed the rebuilding of the city.
The Bank of New Zealand's head of strategy, Stephen Toplis, said the government geological service GNS had warned it could be four years before the shaking settled down.
"This is all part of the same thing and it's going to keep happening."
Bonnie Singh, 28, suffered a broken back and neck in the February quake when the tattoo studio she was working in collapsed around her.
Last night, she said she was still physically and mentally affected by that disaster, and yesterday's tremors sent her "spiralling".
"It so sucks. I was just starting to relax," she said.
"It's definitely put a damper on Christmas ... It's just a sure reminder that it's not over.
"And who knows when and if it will ever be - I don't know how much more we can take."
- additional reporting: Anna Leask, Pattrick Smellie of BusinessDesk
