On April 6, 1580, a magnitude 5.5 earthquake centered under the Strait of Dover rattled England and sent a seismic jolt through London, 86 miles away. Two people were killed in the shaking.

Now seismologists say the great city is overdue for another quake. Same place, same magnitude. But this time, much more damage.

Earthquakes like to strike the same place over and over again. Before the 1580 earthquake, another similar tremor shook the area in 1382. Scientists like Roger Musson, a seismologist at the British Geological Survey, study these historical events to better understand what might happen in the future.

Though big earthquakes with magnitudes above a 5 on the Richter scale are rare in Britain, the country is no stranger to smaller tremors. The Guardian reported:

“The country generally experiences a 3.5 magnitude quake once a year, a magnitude 2.5 quake 10 times a year, and around a hundred 1.5 magnitude quakes every year. Every 10 years the country will feel a 4.5 magnitude quake, and on, average, a magnitude 5.5 every 100 years.”

The largest earthquakes occur at boundaries where tectonic plates grind together, like the magnitude 7 quake that devastated Haiti this past January, Chile's magnitude 8.8 in February, or the magnitude 7 that recently rattled New Zealand.

But Britain sits in the middle of a plate. Earthquakes that occur away from plate boundaries are much less frequent, but can be devastating because they are unexpected. “They are a result of stresses that exist throughout any crustal plate, which can reactivate old local weaknesses inherited from episodes of mountain building many millions of years ago,” Musson said to Discovery News.

Musson explained that this type of earthquake contributes to, “only a small percentage of the total seismicity of the planet, but can be significant because of their proximity to urbanized areas.”

If a big earthquake shakes London, there will be billions of pounds worth of damage. Since 1580, the city has expanded substantially. Though many of the modern buildings in London will likely survive a quake, older structures, including the city’s romantic Victorian houses, probably won't.

When the next quake will occur is anyone’s guess. It could hit this year or in fifty years. But when it does, the best thing you can do to stay safe is, “not run outside,” Musson said. “You may run right into a hail of stones falling off the roof.”