Quake swarm rattles Christchurch

Christchurch's sunny summer evening has been disturbed by a magnitude-4.8 quake hitting just before 7pm.

According to Quake Live, the 15km-deep aftershock is the 48th of a nasty swarm of earthquakes to rock the city today.

Power was restored this morning for about 10,000 Christchurch homes that lost electricity in an earlier 5.5 quake - one of the dozens to hit the city today.

The largest quake - 5.5 - struck 5.45am and was centred 20km north east of Lyttelton at a depth of 15km and followed just five minutes later by a 4.2 and then two 4.1s at 5.54am and 6.06am, a 3.9 at 6.49am, a 3.8 at 7.33am, a 4.1 at 9.01am, a 3.7 at 10.04am and another 3.7 at 10.18am.

Since midday there has been a magnitude 3.3, at 1.49 pm, with a depth of 11 km, and a 3.9 which was 15 km deep. Both were centred 20 km east of the city.

The 5.5 shake took out power to thousands of Christchurch homes in the Shirley, Dallington, Burwood, Spencerville and Richmond areas.

Power distribution company Orion said the tremor caused a transformer at its Dallington substation to trip.

Teams had worked to restore power to the affected area as quickly as possible, while Transpower also checked equipment at its Bromley substation. Power was restored to the affected areas before 8am.

Canterbury Earthquake Recovery Authority chief executive Roger Sutton said that despite the loss of power there did not seem to be any significant further damage.

Everyone just wanted a good night's sleep, he said.

Christchurch Mayor Bob Parker said he had not received reports of any significant liquefaction from the shakes overnight.

He said he had heard that because several of the latest quakes were offshore, some people were concerned about the possibility of a tsunami.

"I'd like to reassure them that this is highly unlikely. The advice we have received from GNS is that the faults offshore are short in length and not likely to generate a significant tsunami," Parker said.

"The sea inundation to land is low risk, probably not more than a storm surge."

In Christchurch the quakes were mainly felt as a strong rolling motion, rather than the short, sharp jolts that tended to do more damage.

Residents needed to remind themselves they should expect more aftershocks, following the 5.5 magnitude shake.

"So just prepare yourself for one of those shaky Canterbury days."

Quakelive has ranked the 5.5 at 5.45am as the 11th largest shake to hit the city.

The city was initially shaken awake today at 1.27am with a 5.1 magnitude quake, again centred 20km north of Lyttelton.

Just four minutes later there was a 4.3 at a depth of 12km and then a 3.5 at 2.20am and a 3.8 at 5.03am. These were all 20km north-east of Christchurch and at depths of 12km, 20km and 8km respectively.

One Twitter user described the 5.1 event as ''like a violent train going through''.

Other Twitter comments included:

"Restless night. These are some serious earthquakes."

"Not laying in bed listening to the birds, laying bed listening to the aftershocks."

"Found myself outside after that one. Don't remember why I ran."

"I can't stopshaking now so I can't tellif the earth's moving or it's just me."

"Got teens out of bed and under a table - so it must have been big!"

There were no immediate reports of further damage or liquefaction, but one Twitter user reported they had lost power.

This morning's shakes followed a magnitude 4 aftershock at 10.05pm yesterday and a 3.5 shake at 7.38pm.

- © Fairfax NZ News