Christchurch continues to be rocked by aftershocks this afternoon, with a staggering 41 earthquakes recorded in the Canterbury region over the past 24 hours.
A swarm of large aftershocks, including a violent magnitude 5.5, rattled the city overnight and knocked out power to thousands of homes.
There have been no reports of significant damage or injury, but it was a sleepless night for most residents as 14 aftershocks - all above 3.3 magnitude - struck at regular intervals between 10.31pm and 9.01am.
The latest shake was a magnitude 3.9 at 12.28pm, at a depth of 15km and located 20km east of Christchurch.
Popular website Quakelive ranked the 5.5 quake at 5.45am as the 11th largest to hit the city since the 7.1 magnitude tremor on September 4, 2010. The mag 6.0 December 23 shake is ranked fourth biggest.
After the 5.45am tremor, power was cut to 10,000 homes across several eastern suburbs, including Shirley, Burwood, Dallington, Richmond, and Spencerville.
A spokesman for Orion Energy said the power went down after a transformer automatically shut itself off, as it was designed to do. Service was restored at 7.41am.
There were no reports of liquefaction or residential damage.
The Canterbury Earthquake Recovery Authority (Cera) said there had not been any further "significant'' damage.
But the agency warned on Twitter that cellphone networks were being overloaded and urged people to minimise their calls and texts.
Christchurch mayor Bob Parker said the latest quakes have "rattled'' residents. But he said they needed to remain calm, and be assured that everything was being done to ensure key services remained operational.
"We have staff on stand-by ready to react quickly if the situation requires it. It's not a great start to a new year, but everyone is working hard to ensure we have a resilient and safe city in the future.
"I've heard that because several of these quakes have been offshore, some people are concerned about the possibility of a tsunami, but 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. The sea inundation to land is low risk, probably not more than a storm surge.''
Anyone feeling distressed or overwhelmed by the aftershocks can call the Canterbury Support Line on 0800 777 846, from 8am to 11pm daily.