There are no immediate reports of damage. The U.S. Geological Survey in Colorado says the quake hit the Queen Charlotte Islands at 11:14 p.m. Sunday local time (0314 GMT) and was centered 96 miles (155 kilometers) south of Masset, British Columbia.
The National Weather Service has issued a warning for coastal areas of British Columbia, southern Alaska, Northern California, Oregon and Washington state.
It says the warning area includes Craig and Sitka, Alaska The USGS says the 7.7-magnitude quake shook the area and was then followed by a 5.8-magnitude aftershock several minutes later.
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