Ruined city protected us - mayor

A vehicle drives through water on Ferry Road near Sumner after the two big earthquakes yesterday. Photo / Getty Images

Fifteen thousand homes are without power in Christchurch this morning, roads, bridges and all schools are closed, as the stunned city once again wakes to the destruction caused by earthquakes.

Miraculously, as in the September 7.1 magnitude quake, no one was killed, though 12 were admitted to Christchurch hospitals and dozens more treated in emergency departments from injuries caused by falling debris after yesterday's magnitude 5.5 shake at 1pm, then a 6.0 jolt at 2.20pm.

Aftershocks continued to rattle the city overnight including a 4.7 magnitude quake which struck at 2.48am, 15km deep and 10km southeast of Christchurch, which caused no further damage, police said.

They also said it was a quiet night in the city as, helped by 30 soldiers, they spent a lot of time patrolling the eastern suburbs. Up to 140 officers from outside the district had been called in to help with policing.

Christchurch Mayor Bob Parker told Radio New Zealand it was "a very rough night in the city".

Yesterday's tremors caused a lot more damage in the central city, already devastated by the deadly February 22 quake. Some buildings there were now condemned beyond doubt.

Tremors also inflicted severe damage on quake-damaged buildings outside the central city, which would now have to be demolished for safety, he said.

"Probably buildings that were borderline are now no longer borderline, their future is clear, they have no future," he said.

The rebuilding process had not been set back, as officials were still gathering information about what could be rebuilt.

"We are still on track, we are still filled with optimism about our future."

Aftershocks were expected and would be part of Cantabrians' lives in the near future, he said.

"We have no control over how long they go on and people need to make their own decisions about what they want to do and whether or not they are going to stay committed to our community.

"What we do know is that it will get better, these will pass and yes, there is an uncertain time.

"But our city, even in this munted state that we find ourselves in, has come through and has protected us."

Christchurch police urged commuters to be patient and careful as they travel around the city's roads, which had again suffered from liquefaction, surface flooding and potholes.

Schools and early child care centres were closed today and police ask other people to minimise their travel as much as possible to ensure infrastructure damage assessments can be done and repairs made.

District commander Superintendent Dave Cliff, said yesterday's quakes vindicated the decision to keep the red zone in the central city closed to the public.

"The falling masonry, bricks and building facades that happened yesterday could have been so much worse if people had been in the CBD at the time."

Initial reports indicated 50 buildings could need to be demolished and many of those were ones hit in the earlier earthquakes.

Lines company Orion's general manager Rob Jamieson said the 2.20pm quake knocked out the power to 56,000 customers, but this morning just 15,000 houses were without power.

The worst damage was in the east - the Sumner and Redcliffs areas.

The company was trying to get as many people back on today but in extreme cases of damage some might be without power for another night, Mr Jamieson told Radio New Zealand.

Water had been restored to about 90 per cent of city.

There was no water supply east of Ferrymead bridge and repairs were expected to take several days, but 90 per cent of people on the flat have water back on. Hills suburbs have low water pressure as teams worked overnight to repair water pipes across the city.

A city wide boil water notice was in place and two water tankers were in the Sumner area. Seven more will be operational this morning.

Authorities were asking people to use portaloos or chemical toilets if they had them. Christchurch's wastewater treatment plant is working but there was more damage to wastewater pipes in the eastern suburbs.

- NZPA