Geoscience Australia said a magnitude 3.3 earthquake off Kangaroo Island on Wednesday night would have been felt across the northern part of the island, but probably not on the South Australian mainland.
The epicentre was in Investigator Strait, about 10 kilometres offshore and about 25 kilometres from Kingscote.
It rattled the area about 8:30pm.
Seismologist David Jepsen said earthquakes in the area were rare.
"There was something back in 2008, that was a little bit smaller than that," he said.
"But if we go back into the 60s there was actually a magnitude 4.6 close by, so that would have been much larger and been felt all over Kangaroos Island plus also some of the other parts of South Australia as well."