Major quake strikes off New Zealand's coast; tsunami warning canceled

(CNN) - A major earthquake struck off the coast of New Zealand's South Island Wednesday night, rattling residents and prompting a tsunami warning that was later canceled.

The 7.8-magnitude quake generated a small, 6-inch tsunami in Jackson Bay, on the west coast of South Island and a 2-inch tsunami reported in the Tasman Sea to the north of the epicenter, according to the the U.S. Pacific Tsunami Warning Center.

Twenty minutes after the temblor, a 5.8-magnitude aftershock struck the same region, according to the U.S. Geological Survey, which measures earthquakes around the world.

Australia has warned residents on an island between its east coast and New Zealand to head to higher ground in case of a tsunami.

The initial quake struck around 8:22 p.m. local time (9:22 a.m. UTC/5:22 a.m. ET) and its epicenter was located 95 miles (150 km) west-northwest of Invercargill, according to the USGS. It is a sparsely populated area of New Zealand.

The aftershock struck in about the same area, according to the USGS.

A tsunami warning was issued for New Zealand as a precaution shortly after the initial quake, but was canceled about an hour and a half later.

The warning center said the tsunamis that were generated "may have been destructive along coasts near the earthquake epicenter."

But, it added, local authorities can assume the threat has passed "for those areas when no major waves are observed for two hours after the estimated time of arrival or damaging waves have not occurred for at least two hours."

Australia's Lord Howe Island - located more than 350 miles (600 km) off its east coast - is under a land and marine tsunami warning, the Australian government's meteorological bureau said. People living in low-lying areas are advised to head to higher ground, while those on the coast should travel inland as a precaution.

So far, there have been no reports of major damage.