More aftershocks have occurred in Canterbury after a swarm of strong quakes overnight.
A magnitude 5.4 quake was recorded at 3.24am on Tuesday. It was 20km south of Darfield, at a depth of 15km.
Another magnitude 5.4 was recorded at 11.40pm on Monday, 20km south-west of Darfield, at a depth of 9km.
These are the same as the most severe aftershock recorded at 4.55pm on Saturday.
A magnitude 5.2 quake was recorded at 11.24pm on Monday, 20km south-east of Darfield, also at a depth of 9km.
The latest quake, at 4.17am on Tuesday, measured magnitude 3.5. It was 10km south-west of Christchurch, at a depth of 7km.
Civil Defence advises residents to prepare for even bigger aftershocks.
CD duty manager John Mitchell says he has been told by geologists that an even stronger quake could occur.
He says it is unlikely the latest aftershocks caused any new damage, but would have undermined the integrity of the buildings that are already damaged.
Mayor Bob Parker says the big aftershocks are causing more damage and fear.
He told Morning Report that the swarm of aftershocks was very frightening and he checked he had his bags backed, as an "ominous feeling" it was going to get worse, set in.
Christchurch is still under a state of emergency after a magnitude 7.1 earthquake at 4.35am on Saturday.
A 7pm - 7am curfew is also in effect. The Army is on duty on the streets of the central city.
More to come - GNS
GNS Science says the aftershocks should reduce over time, but residents should prepare for at least one more strong aftershock.
Natural hazards manger Kelvin Berryman told Nine to Noon that he does not think they are the last of the big aftershocks.
He said that, on average, the largest aftershock is one step down from the main earthquake.
Mr Berryman said the aftershocks will gradually lessen, but could go on for another month.
He said the earthquake is putting pressure on other faults in the region and they are accumulating stress.
