Remote sensors indicated that a sea level rise of almost 7 inches occurred immediately following the 7.6 magnitude temblor.
Violent shaking brought down power lines in the city of Invercargill, and toppled objects and cracked walls in Queenstown and several other communities.
The quake was felt across much of the country, including the city of Christchurch, where buildings shook more than 320 miles from the epicenter. Several aftershocks jolted the region during the hours that followed the initial quake.
One resident of Invercargill told the New Zealand Press Association that the main tremor lasted at least a minute.
Wednesday's quake, which hit at 9:22 p.m. local time, was the largest since 1931, when a temblor the same size on North Island killed 256 people.
It occurred at a shallow depth of only 7.5 miles beneath the surface just off the coast of Southland Province, according to the U.S. Geological Survey.