There’s less rumbling on the surface
Seismologists around the world have noticed the same effect Koelemeijer detected in London, and at more traditional stations than a fireplace.
The trend started with Thomas Lecocq, a seismologist at the Royal Observatory of Belgium, in Brussels. Seismic stations are usually found well outside metropolitan areas, away from vibrations that could obscure subtle tremors within Earth’s interior, but the Brussels station was established more than a century ago, before a city grew around it. Today, it provides a fascinating glimpse of the ebb and flow of a bustling city; Lecocq has found that when it snows, anthropogenic seismic activity decreases, and on the day of a road race, it spikes. Lecocq checked seismic data the day before Belgium began a nationwide lockdown, and then the following morning. The drop in activity, he said, was “immediate.” Right now, daytime in Brussels resembles Christmas Day.
Lecocq shared his approach online, and seismologists in the United States, France, New Zealand, and elsewhere are now seeing the effects of their country’s own social-distancing measures on seismic activity. For seismologists who study seismic signals from Earth’s interior—rather than other sources, including people, animals, even storms—quarantines seem to have made it easier to listen. “Normally we wouldn’t pick up a 5.5 [magnitude earthquake] from the other side of the world, because it would be too noisy, but with less noise, our instrument is now able to pick up 5.5’s with much nicer signals during the day,” Koelemeijer said.