A magnitude 7.7 earthquake struck off the coast of western Canada on Saturday and a tsunami warning was issued, authorities said. There were no immediate reports of damage. The U.S. Geological Survey in Colorado said the quake hit the Queen Charlotte Islands Saturday evening and was centered 96 miles (155 kilometers) south of Masset, British Columbia. The National Weather Service issued a tsunami warning for coastal areas of British Columbia and southern Alaska. It said the warning area included Craig and Sitka, Alaska. The USGS said the 7.7-magnitude quake shook the area and was followed by a 5.8 magnitude aftershock several minutes later.