The two major jolts to hit Christchurch this afternoon were within the range of forecasted aftershocks as modelled by scientists, GNS Science said.
The magnitude 5.5 and 6.0 aftershocks that hit at 1pm and 2.20pm were centred on the coast about 10km south of Christchurch and a short distance south of the fault that ruptured in the 6.3 quake on February 22, killing 181 people.
"These aftershocks were within the existing Canterbury aftershock zone and were within probabilities," said Kelvin Berryman, manager of the GNS Natural Hazards Research Platform.
"This size of events is likely to produce its own aftershock sequence, therefore rejuvenating aftershock activity at least in the short term.
"We would expect a number of aftershocks in the magnitude 4.0 to 5.0 range on the coming days and weeks," Dr Berryman said.
Aftershock activity had not moved offshore on to other faults in Pegasus Bay, he said.
Scientists had being saying since late last year that Canterbury could expected elevated earthquake activity for many months following the magnitude 7.1 Darfield earthquake in September, GNS Science said.
