Lockdown has made the world a quieter place, allowing scientists to hear Earth's deeper rumblings

The incessant industrial hum of humanity halved during lockdown, allowing scientists to hear the deep rumblings of the Earth for the first time since seismic studies began.

Factories fell silent, planes were grounded, traffic levels plummeted and even the footsteps of humans decreased dramatically as billions of people around the globe ceased their usual activity and followed social distancing guidelines.

According to Imperial College London and the Royal Observatory of Belgium, in Brussels, that has led to the longest and most pronounced quiet period of seismic noise in recorded history – even quieter than the annual pause in activity at Christmas.

In total, global seismic noise originating in human activity dropped by as much as 50 per cent from March to May.

The relative silence allowed researchers to listen in to previously concealed earthquake signals, helping to differentiate between human and natural vibrations, which could lead to better predictions of natural disasters such as quakes and tsunamis.

The effects of lockdown are so striking that some researchers have named the drop in human noise and pollution the "anthropause".

Study co-author Dr Stephen Hicks, from Imperial's department of earth science and engineering, said: "This is the first global study of the impact of the coronavirus anthropause on the solid Earth beneath our feet.

"This quiet period is likely to be the longest and largest dampening of human-caused seismic noise since we started monitoring the Earth in detail using vast monitoring networks of seismometers.

"Our study uniquely highlights just how much human activities impact the solid Earth, and could let us see more clearly than ever what differentiates human and natural noise."

Seismic noise is caused by vibrations within the Earth, which can be triggered by earthquakes and volcanoes but also bombs and daily human activity such as travel and industry.

The strongest drops in noise were found in urban areas, but the global quietening was picked up by sensors buried hundreds of feet underground in more remote areas.

Researchers studied data from a global network of 268 seismic stations in 117 countries and found significant noise reductions compared to before any lockdown at 185 of those stations – nearly 70 per cent.

They were able to see a "wave" of quiet spreading from China, to Europe and the rest of the world as lockdown measures took hold.

The largest drops in vibrations were seen in the most densely populated areas, such as Singapore and New York City, but drops were also noted in remote areas such as Germany's Black Forest and Rundu, in northern Namibia.

In the 20th and 21st centuries, seismic noise has gradually increased as economies and populations expanded, making it difficult for scientists to tease apart the different signals and hear natural phenomena that were being masked by human vibrations.

Previously concealed earthquake signals have been heard for the first time, and researchers say the lockdown quietening could open up new fields of research that improves detection of forthcoming natural disasters.

Lead author Dr Thomas Lecocq, from the Royal Observatory of Belgium said: "With increasing urbanisation and growing global populations, more people will be living in geologically hazardous areas.

"It will therefore become more important than ever to differentiate between natural and human-caused noise so that we can 'listen in' and better monitor the ground movements beneath our feet. This study could help to kick-start this new field of study."

Countries such as Barbados, where lockdown coincided with the tourist season, saw a 50 per cent decrease in noise.

"The lockdowns caused by the coronavirus pandemic may have given us a glimmer of insight into how human and natural noise interact within the Earth," added Dr Hicks.

"We hope this insight will spawn new studies that help us listen better to the Earth and understand natural signals we would otherwise have missed."

The research was published in the journal Science on Thursday .