The quake was felt as far afield as Invercargill, Gore, Dunedin and Tekapo.
A second, stronger magnitude 5.7 earthquake struck about about 35km northeast of Milford Sound at 6.57pm,
Residents reported the second shake “felt stronger”.
A third earthquake, measuring magnitude 4.6, struck 35km northeast of Milford Sound at a depth of 5km at 7.12pm, according to preliminary GeoNet data.
Queenstown Lakes District Council said Edith Cavell Bridge will be closed overnight after the earthquakes.
“As this bridge is a historical asset with heritage status, an inspection is required following earthquakes like the one we just experienced.
“Traffic from Arthurs Point will need to detour via Malaghans Rd, Dalefield.
“Engineers will inspect the bridge at first light tomorrow morning and we’ll provide a further update when we know more.”
Motorists have been urged to take care around alpine passes such as Crown Range Rd because there may be debris from the recent earthquakes.