The epicenter was 808 kilometers (502 miles) southwest of Padang, the US Geological Survey said. It was 10 kilometer (six miles) deep.
There were no immediate reports of damage or casualties, but the shallower a quake, the more likely it is to cause damage. USGS originally put the magnitude at 8.2, and then 8.1, before lowering it to 7.9.
“So far there have been no reports [of damage] yet,” Andi Eka Sakya, an official of the National Meteorological Agency, told TVOne. “In Bengkulu [on southwest coast of Sumatra] they didn’t feel it at all.”
President Joko Widodo was staying overnight at a hotel in Medan in North Sumatra and was safe, palace officials said. A Medan resident said he didn’t feel the quake.
Indonesia, especially Aceh, was badly hit by the Indian Ocean tsunami in 2004.
A 9.15-magnitude quake opened a fault line deep beneath the ocean on Dec. 26, 2004, triggering a wave as high as 17.4 meters (57 feet) that crashed ashore in more than a dozen countries to wipe some communities off the map in seconds.
The disaster killed 126,741 people in Aceh alone.
Indonesia straddles the so-called “Pacific Ring of Fire,” a highly seismically active zone, where different plates on the earth’s crust meet and create a large number of earthquakes and volcanoes.