Lockdown caused longest quiet period of seismic noise in Earth's historyChristian Fernsby ▼ | August 3, 2020
The lack of human activity during lockdown caused human vibrations in the Earth to drop by an average of 50% between March and May 2020.
The new research, led by the Royal Observatory of Belgium and five other institutions around the world including Imperial College London, showed that the dampening of 'seismic noise' caused by humans was more pronounced in more densely populated areas.
The relative quietness allowed researchers to listen in to previously concealed earthquake signals, and could help us differentiate between human and natural seismic noise more clearly than ever before.
Co-author Dr Stephen Hicks, from Imperial's Department of Earth Science and Engineering, said: "This quiet period is likely 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."
The paper is published in Science.
Measured by instruments called seismometers, seismic noise is caused by vibrations within the Earth, which travel like waves. The waves can be triggered by earthquakes, volcanoes, and bombs but also by daily human activity like travel and industry.
Although 2020 has not seen a reduction in earthquakes, the drop in human-caused seismic noise is unprecedented. The strongest drops were found in urban areas, but the study also found signatures of the lockdown on sensors buried hundreds of metres underground and in more remote areas.
The largest drops in vibrations were seen in the most densely populated areas but drops were also seen in remote areas. ■