An earthquake expert says there could well be more powerful earthquakes in the coming days.
With hundreds of aftershocks continuing to rock north Canterbury, including a magnitude 6.3 at 1:34pm, GNS Science seismologist Dr John Ristau says there is unfortunately a very real chance of another really big one.
"There is still a reasonable probability that this earthquake could result in or trigger other large earthquakes, like another magnitude 7 or greater earthquake.
"The probability of that happening is still rather small, something like 10 percent in the next week or so."
One only has to look back to the devastating magnitude 6.3 Christchurch earthquake of February 2011 that killed 185 people, which was essentially an aftershock of the 7.1 quake that hit Darfield, to the west, six months earlier.
If you go back to the Napier earthquake of 1931 the evidence is even more damning. A 7.3 aftershock hit the broken city just 10 days after the initial 7.8 earthquake that killed 256 people and injured thousands more.
A magnitude 7.3 aftershock hit Napier only ten days after a 7.8 earthquake devastated the city in 1931(Getty)
"There will be many aftershocks coming and this could go on for weeks and likely for months, and there could be some likely significant sized aftershocks," says Dr Ristau.
"People should be prepared for the small chance of another similar-sized earthquake."
While there have been many smaller earthquakes measured around the country since the big one hit just after midnight, GNS Science says a lot of those actually aren't real.
"They're actually what we call ghost quakes," says Dr Ristau.
"That's when our automatic system gets a bit confused, especially when there's a great number of earthquakes and aftershocks, and it starts to mis-locate earthquakes."
Most of the real aftershocks have been confined to the area along the east coast at the top of the South Island.