Hundreds of countries around the world are now on lockdown, and that means the streets are empty, traffic has slowed to a minimum and fewer people are now traveling. Since billions of people are now asked to stay at the comfort of their own home to help stop the spread of the virus, the world has become much quieter and scientists are noticing it too.
Pandemic is making the Earth shake less
Seismologists are observing less ambient seismic noise around the world. This means that the vibrations generated by trains, cars, buses, and people reduced. Because of the absence of the noise from people and public transportation, the Earth's upper crust is moving a little less.
A geologist and seismologist at the Royal Observatory in Belgium, Thomas Lecocq, first pointed out this phenomenon in Brussels. Brussels had a 30% to 50% reduction in ambient seismic noise since March, exactly around the time that the country started implementing school and business closures and other social distancing measures. That noise level is on par with what seismologists would see on Christmas Day.
The reduction in noise helped Lecocq and other seismologists to detect smaller earthquakes and other seismic events that certain seismic stations would not have registered. The daily hum of city life means that Brussels would not typically pick up on smaller seismic events. Seismologists would rely on a borehole station, which uses a pipe deep in the group to monitor seismic activity.
Seismologists in other cities are seeing the same effects in their own cities. Paula Koelemeijer showed how the noise in West London has been affected, with drops in the period after schools and social venues in the United Kingdom closed and again after a government lockdown was announced.
A Ph.D. student at the California Institute of Technology, Celeste Labedz, showed a graph that presents the drop in ambient seismic noise in Los Angeles. Seismologists say that the reduction in noise is a reminder of the coronavirus that has made more than one million people ill, killed tens of thousands of people around the world and brought the daily lives of humans to a halt.
People are heeding lockdown rules
Lecocq said that the graphs charting human noise are evidence that people are listening to the warnings of authorities to stay inside and minimize outside activity in order to help stop the spread of the virus and to flatten the curve.
"From the seismological point of view, we can motivate people to say, 'OK look, people. You feel like you're alone at home, but we can tell you that everyone is home. Everyone is doing the same. Everyone is respecting the rules," said Lecocq.
The data can also be used to identify where containment measures might not be as affected, according to Raphael De Plaen, a postdoctoral researcher at Universidad Nacional Autónoma de México. He said that the data can be used in the future by decision-makers to figure out if things are done right or not. It is best to make sure that containment measures are done properly everywhere as it is in the best interest of everyone.
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