© Mark MitchellSmoke rises from the collapsed CTV Building on February 22.
The quake struck at 3.29am, and was centred 10km east of Lyttelton, off the end of Godley Head, at a depth of 6km.
GNS Science said the quake could have caused minor damage, and had reports it was felt as far north as Hamner Springs and as south as far as Timaru.
Orion said all power had remained connected following the quake.
Christchurch residents turned to Twitter to share their experiences.
CTV reporter Kineta Knight was one of many who had been shaken awake.
"That must have been a big one. All I can hear is alarms!! Long and rumbly."
Many said it felt bigger than a 4.9.
"I demand a recount! That's the first time a 4.9 has knocked something off my shelves!" Gavin Treadgold wrote.
Newstalk ZB reporter Jo Scott said the quake shook her family awake, and went on for quite awhile.
"It's just been unbelievable that in two days time it's going to be the first anniversary of September 4, and we are still getting earthquakes a year later," she says.
Christchurch has now had 7477 earthquakes since last September's magnitude 7.1 quake.
A second major earthquake resulted in the deaths of 181 people on February 22 this year.
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