A magnitude 5.0 earthquake has hit near Seddon.
The quake hit at 4.09pm, 30km south-east of Seddon.
It had a depth of 8km.
It may have registered as a severe quake with GeoNet, but it appears to have only been lightly felt near the epicentre.
Marlborough District Council emergency services manager Brian Paton says of the 760 people that have reported feeling the quake, only two have rated it as moderate.
He says the vast majority are reporting it as a light shake and he's expecting few or no reports of damage.
According to Civil Defence, there is no tsunami alert for New Zealand.
St John spokesman Ian Henderson has not received any reports of injuries from the quake.
"Obviously the timing of this earthquake - on the fifth anniversary of the Christchurch earthquake - means earthquakes are front and centre of peoples' minds. We urge everyone in Marlborough to make sure their emergency packs are prepared, and to check on their friends, family and neighbours, especially those who are ill, frail or alone."
Originally reported as a 4.9, GNS upgraded the quake to magnitude 5.
GNS seismologist Caroline Holden said it had received 888 reports from people who had felt the quake.
Most felt reports came from Seddon, Blenheim and Nelson at the top of the South Island, and Wellington.
The Kapiti Coast was the furthest north someone had reported feeling the quake and Kaikoura was the most southern.
Ms Holden said it was unrelated to recent quakes in Canterbury.
"There area was quite active in 2013 so it may be related to that or it may be a one-off," she said.
It was unlikely the quake caused much damage as it was offshore, she said.
However, it was likely there would be aftershocks, some as high as magnitude 4, as the quake was quite shallow, she said.
Several Herald readers have reported feeling the quake.
Kerry Hamilton said it was a "rolling [off] the ground-type of quake, rather than one that comes with a bomb".
"I was originally questioning whether my balance was out at first."
Meanwhile, Shelley Avery said lights were swinging and mirrors were rattling south of Seddon.
Another reader said they felt the quake in Lower Hutt, while another felt it at Lyall Bay, Wellington.
On August 16, 2013, an 8km deep magnitude 6.6 earthquake struck just offshore from Seddon. It caused significant damage to houses and infrastructure in the region and sent workers in Wellington running into the streets as the ground shook and buildings swayed from side to side.
Another quake on July 21, 2013, which was 13km deep magnitude 6.5 and centred in the Cook Strait, caused damage to several homes in Seddon and several buildings in the Wellington CBD, with glass from broken windows falling onto Lambton Quay.