The 7.8-magnitude quake exposed gaps in the systems put in place to prevent a disaster similar to the Indian Ocean quake that killed more than 200,000 people 11 years ago.
A series of early-warning buoys deployed after a 2004 tsunami devastated parts of Indonesia's western Sumatra Island were not working when a huge quake rocked the same area on Wednesday, foreign media reported.
The 7.8 magnitude, shallow undersea quake hit late Wednesday off Sumatra, sending panicked residents fleeing for the hills and briefly triggering a tsunami alert.
But a tsunami was not generated and there have been no reports of casualties or major damage, with life largely returning to normal in affected areas on Thursday.
However, the national disaster agency said the process of confirming that a tsunami had not occurred was hindered because none of the country's 22 early-warning buoys were working.
The early part of the warning process ran smoothly, with a tsunami alert quickly sent out to communities across Sumatra, which led to sirens sounding and people heading to higher ground.
But without the working buoys, which can detect changes in water movement and relay the data back to officials, it took authorities around three hours to confirm that destructive waves had not been generated and to call off the alert, foreign media reports.