For a few terrifying seconds, it felt like the big one all over again.

Yesterday's shallow 5.0 magnitude aftershock was powerful enough for many Cantabrians to relive the panic experienced during the devastating 7.1-magnitude quake more than six weeks ago.

While there have been hundreds of aftershocks, some measuring as big as yesterday's, this one felt different.

It had the hallmarks of the main quake - the tears and the screaming, bricks falling from buildings, possessions falling off walls and shelves, power and phone lines going down, buildings being evacuated and land turning to liquid.

The resilience of residents is being tested again.

For some this latest big shake is the last straw, and they are now looking at their options for getting out of the region.

"There have certainly been moments when I'm sure we have all had that thought," said Christchurch mayor Bob Parker.

He said yesterday's aftershock "did remind everybody of the opening moments of the event of September 4.

"But I think every quake has that potential to take us back to that place."

The latest shake was part of an expected pattern, Mr Parker said.

"I do need to emphasise to people that we are still in the middle of a seismic event. It had a beginning, but we are not at the end yet."

The 5.0 aftershock, one of several yesterday, struck at 11.32am and was centred 10km southwest of Christchurch at a depth of 9km.

Civil Defence spokesman Vince Cholewa said it would have been felt as a magnitude 7 quake.

Angela Wasley, whose home is in the badly hit suburb of Avonside, said it widened cracks on her property and opened up new ones.

She was studying when it hit, and hurt her leg diving under a desk.

She immediately thought of her son who was at school.

Christchurch resident Shirin Namjou was driving through Avonhead when the aftershock hit.

"My car was being shaken around and the traffic lights were moving side to side. It was one of the strongest ones we have felt."

Police were called yesterday to four quake-related incidents, but had not received any reports of injuries, Canterbury district commander Superintendent Dave Cliff said.

Officers were called to the Westfield Riccarton shopping centre, which was partially evacuated after the ceiling collapsed in places.

Bricks fell from buildings in the central city.

There were reports of ground liquefaction in the suburb of Hoon Hay, which council workers were checking, and a supermarket and shops had stock shaken off shelves.

Landlines and mobile networks in the region were hit by overloading.

Telecom said the 111 emergency service was operational, although some calls were diverted to Wellington.

St John Ambulance staff said they had not been called to any quake-related injuries, but several panic calls had come in following the aftershock.

Electricity company Orion's general manager of communications, Rob Jamieson, said about 10,000 customers were without power for up to 20 minutes.

Flights into Christchurch International Airport were delayed immediately after the quake.

One flight from Auckland had to circle the airport as engineers checked the runway for cracks.

The runway and terminal were given full clearance and were operating as normal about an hour after the quake.

Christchurch Hospital sustained some minor damage and switched to its emergency generator for a short time, but all its services continued to operate.

The Fire Service said several fire alarms were set off by the quake, but there were no reports of fires.

Continuing aftershocks

The 5.0 aftershock was followed by a 3.7 aftershock, 10km east of Diamond Harbour at 11.41am, at a depth of 5km.

Two 3.4 aftershocks struck just after midday, the first centred 10km south-west of Christchurch struck at a depth of 3km at 12.06pm, followed by one 20km west of Christchurch at a depth of 15km at 12.39pm.

A 3.8 aftershock struck 20km south-west of Christchurch at a depth of 5km at 1.24pm.

At 2.22pm a 3.3 aftershock struck at a depth of 8km, 10km south-west of Christchurch.

A 3.1 aftershock struck 10km south of Christchurch at a depth of 15km at 5.06pm.

A 2.9 aftershock struck 10km east of Darfield at a depth of 7km at 10.07pm.