A "ROARING" 1.5 magnitude earthquake has shaken Brits awake - with locals saying "our wardrobe moved".
Tremors from the Snowdonia quake last Thursday were felt up to 25km away in Gwynedd and Anglesey.
The British Geological Survey said the epicentre of the quake was 12km below ground near Foel Grach in the Welsh mountain range.
Locals told how the 1.5 magnitude earthquake "roared like a strong wind".
Another resident in the quake zone noticed "just a rumble for a few seconds".
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But most people slept through the earthquake at 12.48am last Thursday.
Last month the Scottish Highlands were hit by two earthquakes in the space on nine hours.
But how do earthquakes occur, and where have the strongest ones been recorded?
What causes an earthquake?
The earth's crust is made up of different pieces known as tectonic plates.
These plates fit together like a jigsaw and continuously move at a rate of a few centimetres a year, in different directions and at different speeds.
It's common for plates to slides past each other, bump into each other and move away from each other.
As plates carry on moving in different directions over long periods of time, friction causes energy to build up.
Eventually it becomes so great that the energy is released, which creates a shock wave - an earthquake.
If the earthquake is beneath the ocean it can create a series of huge waves, called a tsunami.
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Earthquakes occur around the world everyday with some so small, they can only be detected using specialist equipment.
Others can be powerful enough to damage and destroy towns and cities.
The size of such earthquakes would be measured on the Richter magnitude scale.
There are earthquakes in the UK, but they are rare and so small that most people do not feel them.
How is magnitude measured?
Magnitude is the most common measurement for the strength of an earthquake.
Typically magnitude will be recorded by measuring the amplitude of seismic waves that are recorded on a seismometer.
Seismometers are instruments that respond to noises and shaking in the ground.
A magnitude readout is typically represented by a small number.
What's interesting about magnitude is that it climbs on a logarithmic base-10 scale.
So each time the number increases by one, the amplitude is actually 10 times greater.
That means that a magnitude 4 earthquake isn't twice as strong as a magnitude 2 quake, but 100 times.
The strongest quake on record peaked at around 9.4 to 9.6 magnitude.