The earthquake was 15km east of Seddon and 11km deep.
A Ministry of Civil Defence spokesman said while there would be "a few pounding hearts" following the rattle, there was no need for people to worry about a tsunami.
"It's certainly not of the size where people would need to be worried about a tsunami risk."
No reports of damage have been made to the Tasman DCC at this point, police said.
One twitter user exclaimed it was "deeply unpleasant" to be in a stairwell during "that sort of nonsense".
Another said the quake wasn't quite strong enough to send them running for cover under a desk, but it nearly was.
Meanwhile in another office, workers did get under their desks. "Under our desks was gross," one of the workers tweeted.
Blenheim local Izzy Tannock was at work at Yealands Estate winery, a short distance from the coast east of Seddon, when the quake struck.
The quake lasted not longer than ten seconds, she said, but it was the biggest she had felt in a while, and enough to rattle her nerves a little.
"It was like a big jolt and then a slower roll," she said.
"I stood up from my desk and waited to see how it panned out, because you can hear them before you feel them.
"You can hear them through the building; it's like a really deep rumble."
She said aftershocks in the area had only just begun to settle down after November's 7.8 magnitude Kaikoura quake.
"I thought 'Oh no, is this going to happen again?' It's a little bit frightening."
Despite the fright, the quake hadn't been big enough to cause any damage or knock any items of shelves.
Source- NZ Herald