A large aftershock shook Christchurch early on Friday.
GNS Science says it was magnitude 4.1, at 0.03am. It was centred 10km south-east of the city centre.
The shock was felt widely throughout the city.
There was a spate of aftershocks around 9pm on Thursday - the largest of which was of magnitude 3.7 at 9.24pm at a depth of 8km.
Two others, measuring 3.2 and 3.3, occurred at 3.35am and 4.58am respectively on Friday.
