(CNN)Once-crowded city streets are now empty. Highway traffic has slowed to a minimum. And fewer and fewer people can be found milling about outside.
Global containment measures to combat the spread of the coronavirus have seemingly made the world much quieter. Scientists are noticing it, too.
Around the world, seismologists are observing a lot less ambient seismic noise -- meaning, the vibrations generated by cars, trains, buses and people going about their daily lives. And in the absence of that noise, Earth's upper crust is moving just a little less.
Thomas Lecocq, a geologist and seismologist at the Royal Observatory in Belgium, first pointed out this phenomenon in Brussels.
Brussels is seeing about a 30% to 50% reduction in ambient seismic noise since mid-March, around the time the country started implementing school and business closures and other social distancing measures, according to Lecocq. That noise level is on par with what seismologists would see on Christmas Day, he said.
Less noise means seismologists can detect smaller events
The reduction in noise has had a particularly interesting effect in Brussels: Lecocq and other seismologists are able to detect smaller earthquakes and other seismic events that certain seismic stations wouldn't have registered.
Take, for example, the seismic station in Brussels. In normal times, Lecocq said, it's "basically useless."
Seismic stations are typically set up outside urban areas, because the reduced human noise makes it easi