Several thousand people were left without power after the quake in the county of Kent, but there were no immediate reports of injuries.
"It literally felt like the whole house was being slid across like a fun-fair ride," said Sharon Hayles of Stanford, southeast England.
The British Geological Survey said the 4.3-magnitude quake struck at 8:18 a.m. (0718 GMT) and was centered at sea, 7.5 miles (12 kilometers) off the Dover coast. The area is about 60 miles (100 kilometers) southeast of London.
The U.S. Geological Survey put the magnitude at 4.7.
Witnesses said cracks appeared in walls and chimneys collapsed across the county. Energy supplier EDF Energy said several thousand homes were without power after the quake, and the fire service was investigating several reports of gas leaks.
Residents said the tremor lasted about 10-15 seconds.
"I was lying in bed and it felt as if someone had just got up from bed next to me," said Hendrick van Eck, 27, of Canterbury, 60 miles (100 kilometers) southeast of London.
"I then heard the sound of cracking, and it was getting heavier and heavier. It felt as if someone was at the end of my bed hopping up and down."
There are thousands of moderate quakes on this scale around the world each year, but they are rare in Britain. Saturday's quake was the strongest in Britain since September 2002, when a 4.8-magnitude quake struck the central England city of Birmingham.
The country's strongest earthquake took place in the North Sea in 1931, measuring 6.1.