“There’s several kilometres of uncertainty in that,” Mr Cummins said on Sunday morning.
Geoscience Australia has received more than 9200 reports from people who said they felt the earthquake, which Mr Cummins said “is substantial”.
There are no reports of any injuries or damage to buildings.
“An earthquake of this size is unlikely to cause substantial damage,” Mr Cummins said.
“The most likely scenario there will be a few more tremors and it will decrease with time.”
Mr Cummins last time there was a 3.8 magnitude earthquake in the area was in 2010.
Smaller earthquakes have been recorded in 2016, 2017 and 2018.
The state has previously experienced a larger seismic event, with a magnitude 5.4 earthquake recorded in Adelaide in 1954.