The relative silence allowed researchers to listen for previously hidden earthquake signals and
Quiet period is probably the longestand the most significant attenuation of anthropogenic seismic noise as scientists began detailed monitoring of the Earth using extensive seismometer monitoring networks.
The study makes it clear how much human activity affects the solid Earth.
The measured seismic noise is caused by vibrationsinside the Earth, which spread like waves. Waves can be caused by earthquakes, volcanoes and bombs, as well as daily human activities such as travel and industry.
No earthquakes were observed in 2020, butthe drop in anthropogenic seismic noise is unprecedented. The most severe falls were found in urban areas, but the study also found blocking signatures from sensors buried hundreds of meters underground and in more remote areas.
Human-generated noise is usually attenuated inquiet periods such as the period of Christmas, New Years and Chinese New Years, as well as weekends and at night. However, the drop in vibrations caused by the COVID-19 lockout dwarfs even those seen during these periods.
Some researchers call this reduction in anthropogenic noise and pollution anthropause. This is the first global study of the impact of coronavirus anthropause on the solid Earth beneath our feet.
To collect data, the researchers studiedseismic data from a global network of 268 stations in 117 countries and found significant reductions in noise compared to any blockage at 185 of these stations. Starting with China in late January 2020, followed by Europe and the rest of the world from March to April 2020, researchers tracked a "wave" of calm between March and May, when restrictive measures were taken around the world.
The most noticeable drops in vibration were in densely populated areas such as Singapore and New York, but were also seen in remote areas such as the Black Forest in Germany and Rundu in Namibia.
Citizen-owned seismometers thattend to measure more localized noise, noted large drops at universities and schools in Cornwall, UK and Boston, USA - 20% more noise reduction than during school holidays.
In countries like Barbados where localizationcoincided with the tourist season, the noise level decreased by 50%. This coincided with flight data, according to which tourists were returning home several weeks before the official closure.
Over the past few decades, seismic noise has gradually increased as the economy and population grew.
The study reports the firstevidence that previously hidden earthquake signals, especially during the daytime, on seismometers in urban areas seemed much clearer during the COVID-19 lockdown.
Loosening the blockage could also help them distinguish between man-made noise and natural signals, which could warn of impending natural disasters, the researchers say.
With increasing urbanization and growing world populationmore and more people will live in geologically hazardous areas. Therefore, it is becoming more important than ever to distinguish between natural and man-made noise so that we can “listen” and better track the movement of the ground under our feet. This research can help start a new area of study.
Dr Thomas Lecoq, lead author of the study from the Royal Observatory of Belgium
The authors of the work hope that their work will lead to further studies of seismic localization, as well as the discovery of previously hidden signals from earthquakes and volcanoes.
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