Citizen-owned seismometers showed significant reductions of noise around schools and universities in places like Cornwall, UK and Boston, U.S.  (Image Credit: Imperial College London)


Seismometers measure seismic waves from earthquakes, volcanoes, and they can pick up vibrations from wind, rivers, ocean waves and human activities. An international team of researchers recently revealed that human-linked vibrations in the Earth dropped by an average of 50% between March and May 2020 due to the COVID-19 lockdown.


According to new research, this quiet period was most likely caused by the worldwide effect of social distancing, service and industry closures, and drops in tourism and travel. This is the most prolonged quiet period of seismic noise in recorded history. Researchers also say that the reduction of seismic noise caused by humans was more definite in densely populated areas. That includes places like Singapore and New York City.


Due to the quietness, researchers could listen to hidden earthquake signals. It also allowed them to differentiate between human and natural seismic noise more clearly.


Co-author Dr. Stephen Hicks, from Imperial’s Department of Earth Science and Engineering, said: “This quiet period is 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.”


Even though there isn’t a decrease in earthquakes this year, the reduction in human-caused seismic noise is unheard-of. Urban areas seemed to have the most substantial drops. However, the study discovered lockdown signatures on sensors buried hundreds of meters underground and in remote places. Such areas include Germany’s Black Forest and Rundu, Namibia.


Human-produced noise tends to dampen during quiet periods. That includes the Christmas and New Year holidays, Chinese New Year, the weekends and overnight. However, the reduction in vibrations as a result of the COVID-19 lockdown surpasses those periods.


This map displays 268 seismic stations in 117 countries. (Image Credit: Imperial College London)


To collect data, researchers looked at 268 seismic stations in 117 countries. It revealed considerable noise reductions after the lockdown occurred at 185 of those stations.


Researchers saw a wave of quietening” as lockdown procedures took effect. This started in late January 2020 in China and carried over to Europe and the rest of the world between March and May.


There were also some large drops around universities and schools around Cornwall, UK and Boston, the U.S. The citizen-owned seismometers noted a reduction in noise 20% larger compared to school holidays. Other countries, such as Barbados, saw noise drops of 50%. This corresponded with flight data that suggested tourists arrived home before the lockdown started.


Scientists have also discovered there is less noise in the ocean as a result of the pandemic. With fewer ships in the ocean, marine life that is highly sensitive to noise will find relief. Networks of underwater hydrophones will give scientists the opportunity to study how mammals’ communication changes when the drone of ships is turned down.


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