A magnitude 7.7 earthquake shook Indonesia's northwest island of Sumatra early Wednesday, triggering a small tsunami, snapping power lines and sending panicked residents rushing for higher ground. There were scattered reports of injuries, but only minor damage in most areas. The quake struck at 5:15 A.M. (2215 GMT) and was centered undersea 125 miles (205 kilometers) northwest of the coastal town of Sibolga in Sumatra at a depth of 19 miles (31 kilometers), the US Geological Survey said. It had earlier said the quake measured 7.8. Indonesia's Meteorology and Geophysics Agency and the Pacific Tsunami Warning Center in Honolulu issued tsunami warnings following the quake, but lifted them two hours later. The meteorology agency said a minor tsunami that at its largest was about 16 inches (40 centimeters) high hit Banyak island, Nias island and Sibolga. Safnil, the head of a fishing village on Banyak, said the wave inundated homes along the beach and damaged several boats but caused no casualties. No tsunami damage was reported elsewhere.