An earthquake measuring 3.4 on the Richter scale was felt in the ocean off the West Coast of Saldanha Bay in the early hours of Tuesday morning.
The minor tremor did not cause any damage to infrastructure nor was a tsunami warning issued.
Several aftershocks were felt in various Western Cape Towns and Cape Town.
Hundreds of Capetonians heard a deep rumbling sound or even experienced rattling windows in the middle of the night.
At about 12:30 AM, a fairly weak earth tremor occurred about 20 kilometres off the coast of Yzerfontein.
The benchmark US Geological Survey officially recorded it as a minor magnitude 3.5 earthquake; 5 km beneath the earth's surface.
According to USGS data, the epicentre was 41 kilometres south of Saldanha.
Capetonians experienced two tremors in late September less than two months ago.
The Western Cape Government says the situation is being monitored and there is no cause for panic.
