A magnitude 4.2 aftershock has struck in Christchurch overnight, GNS Science reports.
The quake hit at 2.58am, and was centred 10km southeast of Christchurch, in Lyttelton Harbour off Gollans Bay, at a depth of 9km.
GNS Science said the quake was felt in the Christchurch area, although also received reports it was felt as far north as Sefton and as far south as Temuka.
The jolt was followed by a magnitude 3.7 quake at 5.06am, 10km southeast of Christchurch at Godley Head, at a depth of 8km.
- NZ Herald staff