Two aftershocks were recorded in Christchurch early on Wednesday morning.
A magnitude 4.0 quake centred 20km west of Christchurch struck at 12.57am, at a depth of 11 kilometres, GNS Science says.
The second, a 3.7 quake, Wednesday, hit in the same location at a depth of 10 kilometres, at 5.10am.
Meanwhile, residents in New Plymouth felt a 3.3 earthquake at 12.17am. It was 20 kilometres deep and was centred 20 kilometres south-west of New Plymouth.