Half the world’s population (about four billion people) have reportedly been ordered to self-isolate in their homes to help prevent the spread of COVID-19. The drastic reduction in human activity has had profound effects on the planet, from reducing air pollution to decreasing the intensity of seismic activity, vibrations rippling through the Earth’s crust. The usual humming caused by trains, trucks, cars, and heavy machinery has stopped, and the ground has settled as a result.
Seismologists from around the world have been reporting noticeable changes in data coming from their highly sensitive equipment. In Belgium, for example, scientists say the amount of ambient human noise has dropped by 30%-50% since the lockdown began. Thomas Lecocq, a geologist, and seismologist at the Royal Observatory in Belgium noticed the change back in mid-March, saying that stillness like that has only ever been observed briefly during Christmas.
Typically, seismologist instruments are located outside of cities, specifically to avoid human-induced vibrations that are strong in urban centers. However, the station in Brussels was built over a century ago, and the city has grown around it. Hence why the dip in seismic activity is so pronounced there.
The quieting of the Earth’s crust may be beneficial to seismologists. The crescendo of machinery rippling vibrations when society is busy can significantly dim background noise and reduce the scientist’s ability to detect other signals of similar frequency – such as volcanic activity or minor earthquakes.
A report published in Nature says that the quieting will improve the tracking of seismic events. Andy Frassetto, a seismologist at the Incorporated Research Institutions for Seismology in Washington DC, said:
You’ll get a signal with less noise on top, allowing you to squeeze a little more information out of those events.
Other cities reporting dips in seismic activity include London and Los Angeles. Take the following tweets, for example:
https://twitter.com/celestelabedz/status/1243306005456289792
Another thing scientists have realized is that measurements showing a reduction in seismic activity mean that people are adhering to social distancing guidelines.
Lecocq told CNN:
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 at home. Everyone is doing the same. Everyone is respecting the rules.
And, if there isn’t a reduction in seismic activity, it means that people are flouting lockdown orders. Raphael De Plaen, a postdoctoral researcher at Universidad Nacional Autónoma de México, pointed that out to CNN saying:
That could be used in the future by decision-makers to figure out, ‘OK, we’re not doing things right. We need to work on that and make sure that people respect that because this is in the interest of everyone.’
Therefore, monitoring data from seismologists now will be helpful to gauge what’s going on in future pandemics.
