If Darwin residents felt the earth move early on Thursday it was because of an earthquake in the Banda Sea region.
Geoscience Australia says the earthquake, measuring between 6 and 6.2 in magnitude, occurred 500 km north of Darwin at 6.10am (AEDT).
"A person from the Bureau of Meteorology in Darwin rang me five minutes after the quake and said 'Oh what's happened'," Geoscience Australia seismologist David Jepsen told AAP.
Mr Jepsen, based in Canberra, said the quake was more likely to have been felt by people living in office or apartment blocks.
The earthquake was 200 km deep and "fairly small" for a quake on the plate margins, he said.
"For a plate boundary earthquake this isn't very large," Mr Jepsen said.
"You have to get into the mid-7s or 8s to be getting large."
The seismologist said earthquakes in the Banda Sea were typically felt in Darwin.
Several months ago Darwin experienced a number of similarly-sized earthquakes.
"Darwin just happens to be in a good place to feel the earthquakes," he said.