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The aftershocks keep coming for Canterbury, with another 3.9 magnitude quake near Christchurch this afternoon following this morning's 5.1 tremor.
The quake hit at 12.26pm, 10 km south-west of the city at a depth of 5km, GNS Science reported.
Another 3.9 magnitude quake also struck at 11.10am, 10km east of the city, at a depth of 5km, one of eight tremors recorded to have struck today.
The swarm of aftershocks come in the wake of a 5.1 magnitude aftershock at 6.01am, 10km south-west of Christchurch, at a depth of 10km, GNS Science reported.
It was widely felt across Canterbury.
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Many residents turned to social networking site Twitter to share their experience.
"I am awake OK! Alarm set for 6 and hit the snooze button. Snooze ended by very large rumbling," wrote NewSolid.
"The return of the shake-us-awake alarm clock. A nice rumble and roll there, just like Mum when you have to get up," wrote Mike Dickison.
"That was a big one. Getting up to see if there was any damage," Isaac Freeman wrote.
After the latest jolt, residents again shared their thoughts.
"I was applying mascara when it happened so now I have mascara on my cheek," wrote Chelsea.
GNS Science seismologist John Ristau said the aftershock was one of the largest to hit Canterbury since the devastating 7.1 magnitude September 4 earthquake.
"This is a little bit larger than the one on Boxing Day," he said, referring to a 4.9 quake which caused further damage to buildings in Christchurch.
It was the first aftershock measuring more than magnitude 5 since October 19, and the eighth largest overall.
There have been 14 reports that this morning's quake was "slightly damaging" and one, in Kaiapoi, of it being "damaging".
"It would be surprising if there has at least not been some damage, even if that is just bricks falling from buildings," Mr Ristau said.
A Fire Service spokesperson said there were no call-outs in the wake of the large aftershock.
Since the 5.1 aftershock this morning there have been seven more recorded aftershocks - a 3.2 magnitude quake at 6.28am, centred 20km west of Christchurch at a depth of 12km, a 3.4 magnitude tremor at 8.02am, 10km south-west of Christchurch at a depth of 10km, a magnitude 4 quake at 8.06am, 15km west of Christchurch at a depth of 15km, a 3.2 quake at 8.14am, 10km south-west of Christchurch at a depth of 15km, and a 3.1 jolt at 11.01am, 10km south-west of Christchurch at a depth of 2km, as well as the 3.9 quakes at 11.10am and 12.26pm.
"There is the chance one of this size will trigger smaller aftershocks, around magnitude three, for the next 12 hours."
Mr Ristau said this morning's aftershock was the 3,907th GNS Science has recorded since the September 4 quake.
"That's actually pretty normal for aftershocks. There have probably been many other smaller ones that we were not able to pick up."
Mr Ristau said seismologists had no idea how long Canterbury's aftershocks would continue.
"At the time [following the September 4 quake] we said it could be months or even a year. It would not be a surprise if we have fives every month for a while yet."