The 5.8 quake was centred 30km north-west of Levin, GeoNet said, and was 37km deep. GeoNet had initially assessed the quake as 5.9.
More than 36,000 people, from the Far North to Dunedin, reported feeling the quake.
Trains in the Greater Wellington region are suspended while crews are doing the visual inspection of the full rail network. MetLink said this would cause significant delays this morning at least.
Buses and trains were being held at their nearest station.
There have been no immediate reports of damage.