Aftershocks from the earthquake on 22 February in Christchurch could continue for a year.
Seismologist John Townend from Victoria University told Morning Report on Monay the 6.3-magnitude quake triggered a sequence of aftershocks that are shallow and close to the city.
A 5.3 magnitude aftershock rattled the city on Saturday.
Mr Townend said he would expect at least half a dozen aftershocks measuring magnitude 4.5 or greater to occur before the tremors eventually diminish.
