Police in Christchurch say the first recorded aftershock for the year on Saturday afternoon, felt longer but less sharp than previous shakes.
Inspector Paul Fremaux described the quake, which measured 4.4 on the Richter scale, as slow and steady.
He says Christchurch residents have felt on edge ever since the main earthquake last September, and aftershocks add to people's feelings of apprehension.
Police have not received calls from people reporting damage, or in need of help, following the quake.
It struck at 2.05pm, 20km west of Christchurch at a depth of 11km.