Wellington and the top of the South Island have been hit by a 6.5 magnitude quake this afternoon.
The quake, which was centred 30km east of Seddon, the site of all the seismic activity in the last couple of days, was 11km deep.
Experts say it is unlikely the swarm of earthquakes which rattled central New Zealand today signals "the big one'' could be on the way, but people should still be prepared.
At least 30 earthquakes have struck since 5am, the largest being a magnitude 5.8 in the Cook Strait between Wellington and Seddon at 7.17am.
There have been seven earthquakes measuring above magnitude 4 since 5am. Most have been centred in the strait off Seddon but there have been quakes further south off Kaikoura and as far north as Wanganui.
It is the second time in three days a severe quake has struck near Seddon - a magnitude 5.7 quake shook the region on Friday - prompting fears an even larger earthquake could be on the way.
But GNS Science seismologist Anna Kaiser said earthquakes of this magnitude were not unusual in the region.
''... When we get one of these events there will be increased seismicity in the region and there's always the possibility of a larger event but it's unlikely,'' she said.
However, she said people should be prepared for a large earthquake striking at any time.
Lea Hayward from Blenheim was in bed when the largest of today's earthquakes occurred.
"I actually felt three this morning and they were all reasonable shakes,'' said
"I think people are [apprehensive], and I've been like that myself - is the big one going to come? I do know a few friends who are going to get their emergency supplies updated, and I myself need to do that.''
Seddon Supervalue owner Kevin Kamat said some items were bounced off the shelves.
"It was certainly quite a big one and quite scary, sure. It lasted a wee while and there were quite a few aftershocks. It seemed quite a bit bigger than the one on Friday.''
Stores around Wellington said while the quakes were unnerving, there was no major damage.
Grandslam Liquor store staff member Robert Henry was surprised nothing was broken at the Brooklyn store.
"It felt kind of bad, but nothing fell down, miraculously.''
The quake forced the temporary closure of Wellington's rail network this morning with services replaced by buses while the tracks were inspected, KiwiRail said.
Train services on the Kapiti Line, Hutt Valley and Johnsonville had since resumed but closures remained in place between Wellington, Waikanae and Masterton.
Wellington City Council spokesman Richard MacLean said there had been no reports of damage to infrastructure .
"We did some building checks on Friday after the first big shake.''
Larger buildings such as the Town Hall may be inspected tomorrow.
"Because the shakes are not getting to a size where they are causing obvious damage, we are just taking things slowly,'' he said.
"If the magnitude increases, then obviously we'll jump into action this afternoon.''
Twitter was full of comments about the quake this morning.
"Oh damn that was scary. Crouched in the doorway still shaking,'' said Laura Vincent.
Rochelle Iti wrote after a magnitude 4.9 aftershock: "Excuse me while I move to Australia before #Wellington becomes the new Christchurch''.
Tobias Brockie: "my parents, who live in chch, have both texted me with concern at first and then scornful dismissal in the wake of that quake.''
Journalist Barry Soper said the quake was "fair rocking''.
"15 floors up when the quake struck: Heather, let's watch from the balcony. Barry: Let's stand under a door jam, oh so boring but safe!''