Christchurch is still recovering from the 2011 earthquake that killed 185 people and destroyed the city center.
New Zealand lies on the notorious Ring of Fire, the line of frequent quakes and volcanic eruptions that circles virtually the entire Pacific rim.
There are no immediate reports of damage from the latest quake.
The Herald newspaper said the tremor was felt all the way to Wellington, where sirens sounded and people fled buildings into the streets, some of them crying.
The US Pacific Tsunami Warning Center said there was no tsunami threat.
A magnitude-7.1 quake struck 169km (105 miles) north-east of Gisborne on the North Island in September, sparking a tsunami warning. It caused some damage to property, but no injuries.