The U.S. Geological Survey said the quake had a preliminary magnitude of 7.6 and struck under the island of Simeulue off the western coast of Sumatra—the region worst hit in the 2004 Indian Ocean tsunami.
Minutes after the quake hit, the Pacific Tsunami Warning Center issued a bulletin saying parts of the Sumatran coast closest to the epicenter were at risk of a possible tsunami. However, it canceled the alert two hours later, saying sea gauges had not detected any large waves.
Rustam Pakaya, the head of the Indonesian Health Ministry's disaster center, said "many" buildings on Simeulue were damaged and three people were killed. He said at least 25 others were seriously injured.
The quake was felt across much of western and northern Sumatra island, witnesses said. Many people fled their homes.
"Everything shook very strongly for more than a minute, and I ran along with the others. I heard people screaming in panic," said Aceh resident Ahmad Yushadi.
Indonesia, the world's largest archipelago with a population of 235 million people, is prone to seismic upheaval because of its location on the "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin. (See map.)
The fault that ruptured Wednesday off the coast of Sumatra is particularly deadly.
A magnitude 9 quake there in 2004 triggered a tsunami that killed more than 230,000 people in a dozen countries. Three months later, an 8.7 quake farther down the fault killed a thousand on the islands of Nias and Simeulue.
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