(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 tremor, 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 150 km (95 miles) 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.
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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 600 km (350 miles ) 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.
The temblor shook buildings in Queenstown -- located about 110 miles northwest of the epicenter -- and scared residents who ran into the streets, according to the New Zealand Herald.
The quake, which was felt across South Island, downed power and phone lines, the newspaper reported.
"It wasn't very violent, more of a rolling feel," Simon Darby, a resident of the inland town of Wanaka, told the Herald. "But it had a power about it -- I ran straight outside into the carpark."
A resident of Invercargill told Television New Zealand that the quake lasted about a minute.
"Things just started to rattle a bit, then the house started to sway," the man told TVNZ. He said he and his wife got their three young children out of bed and huddled under a table during the quake, according to the network.
The quake cracked part of his house around the door frames.
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