Two more earthquakes have occurred near Christchurch early on Monday morning.
Some residents report being woken by a magnitude 4.4 quake at 0.10am on Monday, at a depth of 3km.
And a magnitude 3.0 quake was recorded at 2.01am, at a depth of 6km.
Both were within 5km of Christchurch.
Part of central Christchurch remains cordoned off after a series of quakes damaged 20 buildings on Boxing Day. A guard was maintained overnight.
At least 16 aftershocks were recorded from 2am onwards on Sunday. The strongest was magnitude 4.9 at 10.30am, at a depth of 12km.
Power supplies were temporarily cut and a large shopping centre was evacuated.
Boxing Day is one of the busiest shopping days of the year. A Radio New Zealand in the city says it was pure luck that no-one was injured.
Buildings were exploding, and I thought it was glass but it was rock!, said one witness.
Music shop owner Roger Cleave said the latest shocks did more damage than the big quake in September.
This one was a lot more violent and a lot more stuff has fallen off, he said.
Christchurch City Council has established an emergency operations centre and recalled many personnel from leave to deal with the shocks.
The Duty Seismologist at GNS Science says the latest series of earthquake aftershocks felt stronger than previous aftershocks because of where the earthquake's epicentre was located.
Seismologist John Ristau told Summer Report that large magnitude aftershocks are common a number of months after the main earthquake.
Closures on Lichfield St and Colombo St were lifted on Sunday afternoon.
Hereford St between Oxford Tce and Colombo St opened again to traffic before midnight.
However, closures remained in place overnight in the following locations:
Cashel St (City Mall) from Oxford Tce to Colombo St
Gloucester St from Manchester St to Latimer Square
Manchester St from Worcester St to Gloucester St
Manchester St from Hereford St to Cashel St (existing closure from previous damage)
A number of individual buildings which were damaged remain fenced off.
In a statement, Inspector Derek Erasmus said the overnight cordons would help ensure public safety until further building assessments can be carried out tomorrow.
We need to maintain cordons in these locations because of the potential risk to safety from damaged buildings, including falling masonry and brickwork, and damaged windows, he said.
These cordons will be assessed again tomorrow (Monday) and we hope that we can further reduce the extent of the road closures.
We want to cause the least disruption possible so that activity in the city can return to normal.
4 Sept Big One
A magnitude 7.1 earthquake occurred in Canterbury at 4.35am on 4 September.
A state of emergency was declared and the central business district in Christchurch was cordoned-off for several days. Aftershocks have been occurring ever since.
The state of emergency was in force until 16 September.