Christchurch was shaken by an aftershock measuring 4.9 on the Richter scale on Sunday evening.
The quake hit at 7.21pm, and was located 20 kilometres south-west of Christchurch at a depth of 9 kilometres.
Emergency services said on Sunday there were no reports of any damage so far.
It follows an aftershock measuring 4.7 in the early hours of Sunday morning.
The shallow aftershock occurred at 1.34am, centred 20 kilometres west of Christchurch, and was at a depth of 7km.
GNS Science says Sunday evening's aftershock is the eighth over magnitude four to hit Canterbury this month.
GNS Science duty seismologist Caroline Ashenden says it could be two years before Christchurch is free of aftershocks from the 7.1 quake on 4 September.