GNS Science says aftershocks from a string of quakes in Christchurch on Monday will continue for weeks, maybe months - but they are getting further away from the city.
Some 32 tremors of magnitude 3 or more, including one measuring 5.5, shook the South Island city - most of them centred in Pegasus Bay.
The director of GNS Science's Natural Hazards Research Platform says the shakes were not completely unexpected, as some faults offshore have not de-stressed.
However, Kelvin Berryman told Radio New Zealand's Summer Report programme because Christchurch has already been hammered by quakes since September 2010, new ones are likely to be away from it.
Dr Berryman says in certain areas the aftershocks have tailed off, but in neighbouring areas residual stress has built up, kick-starting another sequence of shocks.
One quake was recorded at 4.30am on Tuesday, measuring 3.8 and located 10km east of Christchurch at a depth of 9km.