Another shallow aftershock near Christchurch shook the city on Wednesday afternoon.
The 3.8-magnitude tremor at 1pm was centred just 5km from the city at a depth of 6km.
A GNS Science duty seismologist says quite intense shaking was felt. There have been several aftershocks since 26 December.
Paul Nicholls from the University of Canterbury's digital media group, who set up the Christchurch Quake Map website, says there has been at least 4200 aftershocks since a devastating 7.1-magnitude earthquake on 4 September last year.