An earthquake which rocked Christchurch on Saturday has been downgraded from magnitude 4.6 to 4.2.
However GNS Science says its epicentre was also three kilometres shallower than first thought and 10 kilometres closer to the city.
The quake hit at 5.14am on Saturday, centred 10 kilometres south-east of the city at a depth of eight kilometres.
It was followed by a 3.4 magnitude shake at 8.04am.
Emergency services say there have been no reports of injury or damage.
There was another magnitude 4.0 quake at 7.31pm on Saturday.
The GeoNet website says the most recent sizeable aftershock in Canterbury was a 5.1 quake a month ago.