About four billion people — roughly half the world's population — have reportedly been told to isolate themselves in their homes to prevent the spread of the coronavirus. And the major decrease in the hum of normal human activity has led to a surprising shift in Earth's vibrations.
Researchers who study the Earth's movement said the mandatory shutdown of transportation systems, businesses and other human activities has correlated with the planet shaking noticeably less than usual. A drop in seismic noise — the vibrations in the planet's crust — is giving scientists the rare chance to monitor small earthquakes, volcanic activity and other subtle tremors that are usually drowned out by the everyday movement of humans.
The quieter vibrations were observed by Thomas Lecocq, a seismologist at the Royal Observatory of Belgium in Brussels, and published this week in an article in the journal Nature. According to Lecocq, such a dramatic decrease in noise can typically only be experienced briefly around Christmas.
Lecocq observed that in Belgium, vibrations caused by human activity have decreased by approximately one-third since COVID-19 isolation measures were introduced by the government. The reduction in noise directly correlates with the closing of schools, restaurants and other public spaces in the country on March 14 and the ban of all non-essential travel on March 18.
While individual human activity such as vehicle traffic or construction sites only cause small movements in the Earth's crust, together they produce a sizable amount of "background noise" that hinder scientists' ability to detect natural events at the same frequency.
Since quarantine measures were introduced, the surface seismometer at the Royal Observatory of Belgium has become more sensitive to quieter seismic activity that it would have previously missed, which could lead to better measurements of small quakes, quarry blasts, storms and crashing ocean waves.