Studies find evidence deadly 2004 tsunami was not the first and likely not the last.
US officials issued a tsunami warning for an area within 1,000km of the epicentre, but the Indonesian tsunami alert was lifted shortly after being issued.
The Hawaii-based Pacific Tsunami Warning Centre (PTWC) had warned that the earthquake had “the potential to generate a destructive regional tsunami along coasts located within a thousand kilometres of the earthquake epicentre”.
Speaking to Al Jazeera, the PTWC spokesman Stuart Weinstein said: “This is a much smaller earthquake than the Sumatra earthquake of December 2004, it is not going to be anything remotely like that.”
The Indonesian state-run Antara news agency said thousands of people fled their homes and hotel rooms in Gorontalo when the earthquake struck at 17:02 GMT.
The 2004 Asian tsunami killed nearly a quarter of a million people, most of them in Indonesia’s Aceh region.
That disaster led to pressure for better tidal warning systems in the region.
Indonesia launched a new hi-tech system on Tuesday, aimed at detecting tidal waves and providing faster alerts.
The $130m system is able to detect an earthquake at sea and predict within five minutes whether it could cause a tsunami.
Susilo Bambang Yudhoyono, the Indonesian president, said at the launch that Indonesia was “living on the edge”.
“Three tectonic plates – the Eurasian, Indo-Australian and Pacific meet here. This kind of disaster can strike at any time,” he said.