The quake, which struck at 12.24pm, was centred 10km west of Christchurch at a depth of 16km, Geonet says.
The quake was felt as far south as Dunedin and as far north as Auckland.
St John Ambulance says it has had no reports of injury from the quake.
"This earthquake is a reminder that we are still in the post-earthquake period in Christchurch and Canterbury,'' said Ian Henderson, St John communications adviser for the South Island region.
"We strongly encourage people to keep an eye out for their friends and family, especially those who are ill, live alone or who are frail.
"This is especially important as we head towards the fifth anniversary of the February 22, 2011 earthquake and earthquakes will be on peoples' minds.''
