A 5.1 magnitude aftershock which struck near Christchurch this morning was one of largest since the September 4 quake, a seismologist says.
The tremor struck at 6.01am, 10km south-west of Christchurch, at a depth of 10km, GNS Science reported. It was widely felt across Canterbury.
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,” adzebill said.
“That was a big one. Getting up to see if there was any damage,” isaacfreeman wrote.
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 over magnitude 5 since October 19.
There have been 14 reports 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 two more recorded aftershocks – a 3.4 magnitude tremor at 8.02am, 10km south-west of Christchurch at a depth of 10km and a magnitude 4 quake at 8.06am, 15km west of Christchurch at a depth of 15km.
There have also been reports of another aftershock around 6.25am, however Mr Ristau said it had not been registered by GNS Science’s equipment.
“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.”