The coronavirus pandemic is making Earth shake
less
Global containment measures to combat the spread of
the coronavirus have seemingly made the world much quieter. Scientists are
noticing it, too.
There's an unlikely beneficiary of coronavirus: The
planet
Harmeet
Kaur
By Harmeet
Kaur, CNN
Updated
0033 GMT (0833 HKT) April 3, 2020
(CNN)Once-crowded
city streets are now empty. Highway traffic has slowed to a minimum. And fewer
and fewer people can be found milling about outside.
Global
containment measures to combat the spread of the coronavirus have seemingly
made the world much quieter. Scientists are noticing it, too.
There's an
unlikely beneficiary of coronavirus: The planet
Around the
world, seismologists are observing a lot less ambient seismic noise -- meaning,
the vibrations generated by cars, trains, buses and people going about their
daily lives. And in the absence of that noise, Earth's upper crust is moving
just a little less.
Thomas
Lecocq, a geologist and seismologist at the Royal Observatory in Belgium, first
pointed out this phenomenon in Brussels.
Brussels is
seeing about a 30% to 50% reduction in ambient seismic noise since mid-March,
around the time the country started implementing school and business closures
and other social distancing measures, according to Lecocq. That noise level is
on par with what seismologists would see on Christmas Day, he said.
Less noise
means seismologists can detect smaller events
The
reduction in noise has had a particularly interesting effect in Brussels:
Lecocq and other seismologists are able to detect smaller earthquakes and other
seismic events that certain seismic stations wouldn't have registered.
Take, for
example, the seismic station in Brussels. In normal times, Lecocq said, it's
"basically useless."
Seismic
stations are typically set up outside urban areas, because the reduced human
noise makes it easier to pick up on subtle vibrations in the ground. The one in
Brussels, however, was built more than a century ago and the city has since
expanded around it.
The daily
hum of city life means that the station in Brussels wouldn't typically pick up
on smaller seismic events. Seismologists would instead rely on a separate
borehole station, which uses a pipe deep in the ground to monitor seismic
activity.
"But
for the moment, because of the city's quietness, it's almost as good as the one
on the bottom," Lecocq said.
Seismologists
in other cities are seeing similar effects in their own cities.
Paula
Koelemeijer posted a graph on Twitter showing how noise in West London has been
affected, with drops in the period after schools and social venues in the
United Kingdom closed and again after a government lockdown was announced.
Paula
Koelemeijer
@seismo_koel
How the
seismic noise on our little @raspishake seismometer running in West London
(Twickenham) has been affected by the #covid19UK lockdown. This is a month of
data for station R091F. The average noise levels are down reflecting fewer
trains, buses and cars.
Still,
seismologists say the reduction in noise is a sobering reminder of a virus that
has sickened more than one million people, killed tens of thousands and brought
the normal rhythms of life to a halt.
It shows
people are heeding lockdown rules
Lecocq said
the graphs charting human noise are evidence that people are listening to
authorities' warnings to stay inside and minimize outside activity as much as
possible.
"From
the seismological point of view, we can motivate people to say, 'OK look,
people. You feel like you're alone at home, but we can tell you that everyone
is home. Everyone is doing the same. Everyone is respecting the rules,'"
he said.
The data
can also be used to identify where containment measures might not be as
effective, said Raphael De Plaen, a postdoctoral researcher at Universidad
Nacional Autónoma de México.
"That
could be used in the future by decision makers to figure out, 'OK, we're not
doing things right. We need to work on that and make sure that people respect
that because this is in the interest of everyone.'"
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