A GNS seismologist says the magnitude 5.5 earthquake in Christchurch on Sunday night did not come as a surprise.
The quake happened at 8.34pm. It was centred 10km east of Lyttelton Harbour at a depth of 12km.
It was in the same area as four small quakes, which occurred in quick succession on Saturday.
Seismologist Caroline Ashenden told Morning Report that geologists are still predicting the odd quake that is greater than magnitude 5.0.
But she said their frequency will decrease over time.
The Canterbury Earthquake Recovery Authority says the earthquake brought down some loose masonry and brickwork in the red zone in inner Christchurch.
But engineers have now assessed the area and given the all clear for contractors to resume work.
Police say they have had no reports of damage.