Christchurch was rocked by a magnitude 4.2 earthquake on Thursday morning.
The quake, which was 9km deep, occurred at 4.21am about 20km west of Christchurch.
GNS Science has described the earthquake as strong.
The quake was followed by another at 5.50am of magnitude 3.2.
It was also located 20km west of the city, at a depth of 12km, and GNS Science describes it as moderate.
