The faults were found running below the capital and have the potential to cause damage.
Researchers from Imperial College discovered the fault lines – one running under central London and another below Canary Wharf.
Luckily, experts from the London university said there is only a one in a thousand year chance of an earthquake hitting.
The two faults are moving at a rate of 1 or 2mm a year.
This is a radical u-turn on the traditional view that London is geologically stable.
Dr Richard Ghail, a specialist in civil and environmental engineering at Imperial College, told the Mirror: “It now looks a modestly active, very heavily faulted, complicated area.
“It’s probably gone from the simplest to most
Dr Ghail added that the possibility of an earthquake hitting the capital was “enough to be scary but not fundamentally a problem”.
It would be around 5.0 magnitude but there is a slim chance of a 6.0 magnitude quake which could damage buildings.
The faults were found using radar and the findings are set to be used to draw up guidelines for new buildings in London.
They will be designed to withstand 6.5 magnitude tremors in order to be safe.
There’s a very slim chance an earthquake will stick London – there has not been one since the 1700s.
Researchers also found that London and the south-east is being squeezed by tectonic forces – causing the area to rise at a rate of 1-2mm a year.
Earthquakes have been known to hit the UK.
In 2008 Market Rasen was struck by the biggest earthquake in 25 years.
It measured 5.2 on the Richter scale with tremors felt up and down the country.
