There were more earthquakes in Christchurch overnight. The biggest was magnitude 4.7 at 2.48am on Tuesday.
It was 15km deep and within 5km of Lyttelton.
Two others measuring magnitude 3.2 and 3.8 were recorded at 1.42am and 0.43am respectively. They were 9km and 8km deep, 10km east and south-east of Christchurch.
An earthquake measuring 6.0 occurred at 2.20pm on Monday at a depth of 9km. There have been 28 quakes since then.
It was preceded by a short, sharp jolt of magnitude 5.5 at 1pm.
Canterbury has been hit by strong earthquakes since 4 September last year when a magnitude 7.0 quake occurred, followed by the 6.3 quake on 22 February which killed 181 people and caused severe damage to central Christchurch.
Some buildings already damaged in the February quake and due for demolition collapsed on Monday.
The Canterbury Earthquake Recovery Authority estimates that up to 50 buildings in the city centre were damaged or have collapsed.
Many roads and bridges around the city are closed.
An estimated 20,000 people are still without power.
Christchurch City Council says water has been restored to 75% of the city.
It says water tankers will be stationed around the city today with fresh water.
Forty-six people were treated at Christchurch hospital on Monday. Two remain in a serious condition.
Hospitals have postponed all elective surgery and outpatient appointments scheduled for Tuesday.
All schools are closed.