A magnitude 4.8 earthquake has jolted many Southlanders awake.
GNS Science says the quake happened at 6.36am and was centred 40km northeast of Milford Sound.
GNS Science seismologist Caroline Holden says there have been more than 100 reports from people who felt it, throughout Southland and the West Coast.
Ms Holden says the quake was just 2km deep and was generated in an area where the Pacific plate meets the Australian plate and causes frequent tremors of magnitude four and above.
Quakes in the area rarely cause damage because of their remote location.