Good vibrations? COVID quiet time soothes Earth's seismic shakes
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[July 24, 2020]
By Kate Kelland
LONDON (Reuters) - COVID-19 lockdowns
worldwide led to the longest and most pronounced reduction in
human-linked seismic vibrations ever recorded, sharpening scientists'
ability to hear earth's natural signals and detect earthquakes, a study
found on Thursday.
Vibrations travel through the earth like waves, creating seismic noise
from earthquakes, volcanoes, wind and rivers as well as human actions
such as travel and industry.
In the study, published in the journal Science and conducted using
international seismometer networks, scientists found that human-linked
earth vibrations dropped by an average of 50% between March and May this
year.
"The 2020 seismic noise quiet period is the longest and most prominent
global anthropogenic seismic noise reduction on record," they wrote. The
work was co-led by the Royal Observatory of Belgium and five other
institutions using data from 268 monitoring stations in 117 countries.
Beginning in China in late January, and followed by Europe and the rest
of the world in March to April, researchers saw "a wave of quietening"
as worldwide lockdown measures to slow the coronavirus pandemic took
hold.
Travel and tourism were all but halted, millions of schools and
industries closed, and many people were confined to their homes.
The relative quiet allowed scientists to "listen in" in more detail on
the earth's natural vibrations, said Stephen Hicks, a seismologist at
Imperial College London who co-led the work.
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A working seismograph is shown in a display about earthquakes during
the Great ShakeOut Earthquake Drill at the Discovery Cube Science
Center in Santa Ana, California, U.S. October 18, 2018. REUTERS/Mike
Blake/File Photo
"It has yielded a new window on the natural seismic signals, and
could let us see more clearly than ever what differentiates human
and natural noise," he said.
The study said its findings also showed that seismologists can help
establish how long people take to react to the imposition and
lifting of lockdown measures.
The largest drops in human-induced vibrations were seen in densely
populated areas like Singapore and New York City, but drops were
also seen in remote areas like Germany’s Black Forest and Rundu in
Namibia. Barbados, where lockdown coincided with the tourist season,
saw a 50% drop in seismic noise.
(Reporting by Kate Kelland, editing by Philippa Fletcher)
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