Reports are flying around the Internet right now of two faults having been discovered under London. Although this may sound fairly worrying for those residing there, don’t panic: the scientists who made the discovery certainly aren’t.
These two faults – one found beneath central London and another beneath the Canary Wharf area – are moving at a pace slower than the growth of your fingernails over a year.
Dr Richard Ghail, a specialist in civil and environmental engineering at Imperial College, and part of the team that researched these faults, told reporters that an earthquake could occur at either, perhaps as a 5.0M event. However, he was careful to note to The Telegraph that this was “enough to be scary but not fundamentally a problem.”
This isn’t actually a new discovery. The faults were identified several years back, as described by papers led by Ghail and colleagues. That means, of course, that they have had a decent amount of time to study them and let us know if we should be concerned. Turns out we shouldn’t be – but their discovery does bring with it some curious revelations.
“The faults were initially inferred from geomorphology – drainage patterns, etc. – [along with] borehole records, and site visits,” Ghail told IFLScience. He noted, though, that they “detected their motion using satellite Persistent Scatterer Interferometry (PSI) radar data,” a technique that tracks even small changes in displacement over time.
Ghail explained that the faults are strike-slip faults, similar to many other deep basement faults in the UK. If there was a significant earthquake at any point, we’d expect it to be focused at a depth of around 10 kilometers (6.2 miles) – typical of most UK quakes.
Reports are suggesting that the risk of a 5.0M tremor is one-in-1,000 years, which actually means there’s a 0.1 percent chance of it happening at any given year. However, Ghail told us that the 1-in-1,000 year risk has "not yet been calculated. It is estimated from historical records and activity rates on other faults in the UK.”
The recent reports on these faults, in fact, give us a chance to reassess how we seismologically describe the UK. Although not known for earthquakes, the British Geological Survey (BGS) reminds us that they do occur.
The largest occurred in 1931, some distance offshore, registering as a 6.1M tremor. Hundreds of small quakes take place each year, but mainly on the western side of the British mainland.
“The driving forces for earthquake activity in the UK are unclear,” the BGS explains. “However, they include regional compression caused by motion of the Earth’s tectonic plates, and uplift resulting from the melting of the ice sheets that covered many parts of Britain thousands of years ago.”
The data on these two London faults will be used to reassess the standards applied to buildings in the capital, should a quake ever take place.
“We contend that London, and indeed the whole UK, should be regarded as seismically active, and that building codes should reflect this,” up to a maximum magnitude of 6, even if 5 is far likelier, Ghail said.
“The long return periods and low damage potential of these earthquakes means that codes can be introduced and building stock brought to these standards through the process of natural renewal over the next several decades.”
So: don't panic, dear readers.