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.

An open source online map has been set up to help Cantabrians find help nearest to them.

Stricken homeowners and workers will start receiving compensation and emergency payouts within days as Christchurch's earthquake bill threatens to exceed $2bn.

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

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.

Peter Dunne's bill is unfair, unaffordable and unlikely to happen, writes Brian Fallow.

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

New Zealanders are yet to support infrastructure development to meet future demand, National Infrastructure Advisory Board chairman Dr Rod Carr says.

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.