Indonesia National Meteorological Agency gave an alarm for a potential tsunami in the large area including the western and northern Sumatra, as well as Aceh.
Although there have been no immediate reports of damage for the region, the quake's depth of 10 kilometres which is close to the ground increases fear of a serious damage.
The earthquake's epicentre was 808 kilometers to central Padang of Sumatra, said the USGS.
The USGS initially announced the quake as 8.2 magnitude, than declined it to 8.1. According to last updates, the magnitude was reduced to 7.9, then 7.8.
Indonesia is known to be situated in the “Ring of Fire”, where a large number of earthquakes and volcanic eruptions occur.
Neighboring Australia also issued a tsunami warning for sailors in the western coast, Cocos and Christmas islands far from the mainland.
A tsunami after the 9.1 and 9.3 magnitude deadly quake in 2004 have killed 230 thousand people in 14 countries, around the Indian Ocean and Pacific Ocean.