COVID-19 has hushed human noise to record lows. Here’s why it matters for earthquakes
The hustle and bustle of an average day is usually pretty loud depending on where you live: cars honking on the road, construction workers banging on concrete for hours on end and people shouting over said noise to talk to someone next to them.
But new research says lockdowns during the coronavirus pandemic have hushed the world, leading to a drop in human-caused vibrations felt in Earth by an average of 50% — the quietest humankind has been in recorded history.
A team of international scientists says the quietude is likely the product of social distancing measures, business closures and drops in tourism and travel, according to a news release by the Imperial College London that contributed to the research.
The changes in behavior have given researchers the chance to listen to earthquake signals usually clouded by human activity that could help seismologists decipher between a real threat and a bluff indicator of human behavior.
A study was published last week in the journal Science.
“With increasing urbanisation and growing global populations, more people will be living in geologically hazardous areas,” study lead author Dr. Thomas Lecocq from the Royal Observatory of Belgium said in the news release. “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.”
Decades of monitoring vibrations felt within Earth with sensors buried hundreds of meters under ground have shown that seismic noise is gradually increasing over time as economies and populations grow.
This kind of noise travels in waves and is typically triggered by earthquakes, bombs, volcanoes and human activity such as travel, which is why some researchers have coined the longest and most pronounced silence recorded “anthropause.”
Human noise usually clams down during holidays, weekends and night time, but “the drop in vibrations caused by COVID-19 lockdown measures eclipse even those seen during these periods,” the researchers said in the release.
The team studied data from 268 seismic stations in 117 countries and found that between March and May, noise dropped in 185 of those stations, according to the study. The “waves of quietning” began in China around late January, with Europe and the rest of the world following in March as lockdowns went into place.
The strongest drops occurred in densely populated urban areas such as Singapore and New York City, the researchers said, but they also happened in more remote areas in Germany and Namibia in Southern Africa.
Uncommon bouts of quiet were also detected around schools in Boston and in Cornwall, England — noise drops that were 20% larger than those during regular school holidays, the release said.
As well, countries such as Barbados, where tourism is rampant, saw a 50% decrease in noise, a trend that aligned with flight data that showed tourists flew home weeks before official lockdowns.
“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,” study co-author Dr. Stephen Hicks from Imperial’s department of earth science and engineering, said in the release. “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.”
