Another strong earthquake occurred near Christchurch on Friday morning.
The magnitude 5.1 quake was at 5.39am. It was centred 40km west of the city, at a depth of 12km.
A Selwyn resident has described it as as violent shaking for about seven seconds.
The inner-city red-zone in Christchurch is now open again to contractors.
Canterbury Earthquake Recovery Authority says it is standard practice to close the area with any large aftershock.
The authority has checked a cross-section of buildings for damage and deemed it safe enough for demolition work to resume.
Geonet seismologists say the earthquake was felt along the east coast of the South Island from North Canterbury to Dunedin.
Geonet says the tremor was centred on the Greendale fault, which was at the centre of the magnitude 7.1 quake on 4 September last year.