There were also reports in north Wales, with some claiming they felt the tremor in Broughton, Flintshire, and Llangollen, Denbighshire.
This quake has been felt across a large area of Wales and England with the furthest reports so far from Birmingham and Devon.
"Events of this magnitude only happen in the United Kingdom every 3-5 years".
Early indications a 4.2-magnitude natural disaster struck near Swansea at around 2.30pm this afternoon.
The epicenter was located about 20km - 12 miles - north-north-east of Swansea, said the British Geological Survey.
"An quake of this size, of magnitude five or thereabouts, will occur roughly every 10 to 20 years in the UK", Brian Baptie of the BG said at the time.
Tim Johnson also posted: "Anyone else just feel an natural disaster then?"
"I was sat writing in the loft when the table, computer and whole floor shook for a couple of seconds".
Young blogger Bambino Becky happened to be recording a video when the quake struck, and caught footage of the moment it hit.
The epicentre was just 10km from Swansea but shocks were felt from Cornwall to Blackpool.
There were no reports of any injuries or damage caused.