At least 22 commercial properties and 50 homes in the small quake-damaged North Canterbury town of Kaiapoi have been deemed unsafe, with its mayor admitting the town is changed forever.

Most schools in the quake-devastated Canterbury region are not likely to open until Monday, the Education Minister says.

The final bill for the Christchurch earthquake may reach $4 billion, almost double initial estimates, Treasury Secretary John Whitehead said afternoon.

Aftershocks are continuing to hit Canterbury with one measuring 4.1 the latest in a series today that also included a 5.1.

Mayor Bob Parker says Christchurch city is coping "amazingly well" with the continuing fall-out from Saturday morning's earthquake.

The Government has set aside $2.4 million for trauma counselling for Christchurch earthquake victims, Paula Bennett says.

The state of emergency in Christchurch has been extended a further seven days following an aftershock of 5.1 on the Richter scale this morning.

Rebuilding up to 100,000 damaged and destroyed homes in quake-hit Canterbury could take years, a building executive says.

The Christchurch earthquake is expected to provide a much-needed lifeline for NZ's beleaguered construction sector.

Allan Hubbard believed his self-righteous hype - sadly, so did we.

Christchurch was "inevitably going to be brought to its knees" by an earthquake because of the nature of the ground it stands on, a scientist says.

"It's essentially a ghost town. You can see utter devastation," said Prime Minister John Key.

"It was like a giant had picked up our house and was just shaking it, shaking and shaking," said one resident.

The Govt has announced details of a new 'Savings Working Group' designed to come up with ideas to improve NZ's savings record.

Legislative roadblocks hindering the efficient operation of public-private partnerships are being removed, writes Michael Weatherall.

Fund manager Peter Coman says the PIP Fund is interested in investing in the new Wiri prison public-private partnership but not if it includes managing prisoners as part of the package.