The 4.6-magnitude quake was centered 340 miles (547 kilometers) southwest of Sumatra island, just 6 miles (10 kilometers) under the ocean floor, said Apriliyanto, an official at the country's meteorology and geophysics agency.
Earlier the agency put the magnitude at 6.5, sending out alerts to officials and journalists by mobile phone text message.
A glitch in the agency's computer was responsible for the error, Apriliyanto said.
Indonesia straddles a series of fault lines that make the vast island nation prone to volcanic and seismic activity.
