However, GNS Science later revised the magnitude down and updated its location to 30km west of Arthur's Pass.
The quakes had caused no infrastructure damage. More than 3000 people from Mandeville in Southland to the central North Island reported feeling the quake.
Seventeen insurance claims had so far been lodged with the Earthquake Commission, mostly from residents in the Christchurch and Canterbury areas, a spokeswoman said.
Among those shaken by the quakes was Kiwi actress and former partner of Sam Neill, Lisa Harrow, who said she was lying awake in her Port Levy home about 6.30am when she felt the quake hit.
"Just after that I felt the bed rocking as if I was on a boat in a big swell.
"I experienced the recent earthquakes in the Christchurch area so my immediate thought was, oh, that was another earthquake."
However, Ms Harrow said it wasn't violent enough to stir her sleeping husband, whale biologist Roger Payne.
KiwiRail closed some of its South Island rail lines but yesterday afternoon clearance was given on the final two lines, Stillwater and Midland.
GNS said it was unlikely the quake would trigger another, stronger quake greater than magnitude 7.0 on a separate fault line.