The recovery from Saturday morning's devastating 7.1 magnitude quake, which was today termed a "once-in-750-year event" was set back today when the strongest aftershock yet, of 5.1, jolted the region just before 8am, causing further damage and fraying nerves.
In all, Canterbury has received 270 aftershocks or magnitude 3 or above so far since Saturday's quake, with GNS Science seismologist Brian Ferris said people would have felt about 150 of them.
The state of emergency in the Canterbury region was extended by Civil Defence authorities until next week.
Treasury gave an estimate of $2 billion at the weekend, but its secretary, John Whitehead, told media this afternoon that was in relation to Earthquake Commission (EQC) liabilities only.
"The cost faced by the EQC, individuals, and insurance costs will probably be of the order of $4 billion," Mr Whitehead said.
Christchurch is poised for a rapid recovery effort to swing into action but the cabinet minister in charge, Gerry Brownlee, warned it would not be a "bonanza for cowboys".
The Government is looking at fast-tracking the process so that people can engage contractors and tradesmen and get on with the repairs. An announcement will be made on Friday.
But Mr Brownlee said: "This is not going to be a bonanza for the cowboys. It requires high integrity and it needs the sort of commitment we know local and outside tradesmen can give to the project."
He told media in suburban Sydenham that in the larger Christchurch commercial area, 678 buildings had been checked and 70 percent were determined to be safe. Some were badly damaged but some of those only needed a little more work to ensure they were safe to enter.
Mr Brownlee said he and his government colleagues had met the Earthquake Commission, local authorities, and various other bodies to determine a process for the rapid repair and settlement of outstanding liabilities on damaged properties. The outcome would be in the Friday announcement.
With the quake now seen as a once-in-750-year event, there was always a prospect of it happening again but the known incidence was quite low.
"The on-going confidence that people can have about rebuilding is extremely high in my opinion."
An internet site at www.canterburyearthquake.govt.nz is keeping people up to date with developments.
Thirty-six more Earthquake Commission engineers were expected in the region in the next couple of days, and the commission would have 10 field offices around the region so that people could make direct contact.
Mr Brownlee said reconnections for power, water, and waste water were going well.
The Inland Revenue Department had agreed to take a "realistic and sympathetic" view where businesses were struggling with tax payments.
Wage assistance arrangements offered by the Government had so far been taken up by 99 firms.
ACC had provided 20 call-centre staff to support the Earthquake Commission's help line.
"If there is anything positive to come out of this it is the prospect of having a better, brighter city than we had before. Eighty percent of the city is functioning and undamaged."
He urged people to "find that Crusader spirit", saying: "We can come out of this really well if we do it right."
Prime Minister John Key today visited rural areas, included Kaiapoi and Selwyn, which suffered major damage in the quake. He and other ministers were shown houses which had crumbled or been ripped from their foundations, as well as extensive damage to farms.
Speaking to the media outside a devastated church in Hororata, 56km west of Christchurch, Mr Key said the extent of the destruction throughout the region was clear.
"We always knew things were bad, but I think it shows you how big the rebuild job will be and also what the aftershocks are doing," he said.
"The first thing we've got to do is get the region stabilised and once we have done that we can really start the rebuild job because, unfortunately, some work that had been completed is having to go back and be redone now," Mr Key said.
The situation for those who had lost uninsured homes in the quake was difficult.
"There may be ways through that. Internationally, it's been dealt with in other countries.
"Obviously, our big concern is that we don't want to send the wrong message. New Zealanders have to take insurance, both contents insurance and home insurance, to make sure they are covered in a situation like this."
Civil Defence director John Hamilton said following the big jolt this morning that some inspected buildings would require re-assessment.
Lyttelton Tunnel was closed while cracks were inspected, but it was later re-opened when the New Zealand Transport Agency decided it was structurally safe and sound.
Christchurch Mayor Bob Parker said the city was coping "amazingly well", while reiterating that people should talk to each other for support.
Electricity supplier Orion estimated there were still several hundred customers without power but the number was declining and the company hoped to have it restored to all by the end of the week.
Householders still without power should call Orion on 03 3639898.
