Northeast of Christchurch, The new tremor struck at 13:45pm local time (00:45 GMT) at a depth of 10km (6 miles).
Triggering tsunami warnings, A 7.5-magnitude quake, had hit the same area just after midnight.
A large river dammed up by a landslide has now breached its banks sending a “large wall of water” downstream.
One of the largest on South Island – Residents around the Clarence River – are being urged to move immediately to higher ground.
Since the initial quake, Causing power shortages and cuts in water supply, There have been hundreds of strong aftershocks.
Authorities have been rescuing and evacuating residents along the east coast.
The first earthquake was actually two related tremors, GeoNet, a government-funded project monitoring earthquakes and that aftershocks would continue over the next few weeks and months.
The younger woman’s husband died. After the house collapsed in the first earthquake, a 100-year-old woman and her daughter-in-law were pulled out alive from their home in the town of Kaikoura, New Zealand media reported.
Southwest of Kaikoura, A woman also died at Mount Lyford, though there are reports she may have died from an existing medical condition.
Authorities have since lifted the tsunami alert, but are still warning people to stay away from the shoreline. Waves of around 2m (6.6ft) hit the coast shortly after the first earthquake.
ome schools in the affected area have remained closed on Monday. Residents in Christchurch and surrounding towns have rushed to stock up on basic supplies.
Kaikoura, saw its main road blocked by landslides, water and power supplies cut off.
“He believed the number of fatalities would remain low,” Prime Minister John Key surveyed the affected areas by helicopter and told reporter.
“it looks as though it’s the infrastructure that’s the biggest problem, although I don’t want to take away from the suffering” Civil defence minister Gerry Brownlee told Radio New Zealand.
“The low number of fatalities may be due to the fact that the first quake struck in the middle of the night,” One expert told TVNZ.
Ken Elwood from the University of Auckland said, “People were safe in their homes, homes might get damaged but they’re safer for the people inside and that’s certainly the blessing of this earthquake.”
The quake was also felt in Wellington on the North Island.
“Workers were moving through the city clearing debris and making sure buildings were safe,” Resident Adam Roland told the BBC.
He said, “The CBD’s been closed off so most people are either working from home or not working today.”
Christchurch is still recovering from a 2011 earthquake that killed 185 people and destroyed the city centre.