The Earthquake Commission says a magnitude 5.5 aftershock on Sunday night in Christchurch will be treated as a new event for insurance purposes.
The earthquake was centred 10km east of Lyttelton Harbour at a depth of 12km.
Police have had no reports of adverse effects.
However, the commission says anyone who has new or worsened damage will need to lodge a new claim by early January 2012.
It says more than a dozen aftershocks have been classified as new events since the first quake on 4 September last year.