With Many Countries Under Shelter-in-Place Orders, the World Shakes a Little Less
Geoscientists noticed the normal rumbles of human activity picked up by their instruments have died down as much of the world ground to a halt
The COVID-19 pandemic has shaken up the world, but containment measures are actually making the Earth’s crust shake a little less. Researchers who monitor the planet’s seismic activity to detect earthquakes and volcanic activity have noticed things quieting down as trains, buses and people stop moving around, Elizabeth Gibney reports for Nature.
The drop in seismic noise, or the background vibrations reverberating through Earth’s crust, might improve the accuracy of detection equipment such as seismometers, enabling scientists to pick out small earthquakes and more minute volcanic rumblings.
“It’s very literally reflecting a slowdown of our lives,” Paula Koelemeijer, a seismologist with the Royal Society in London, tells Marina Koren at the Atlantic. “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 says she briefly “geeked out” over the data but her “wow” moment was swiftly overshadowed by the cause of the less-noisy seismographs: a global pandemic that has killed tens of thousands of people, led millions to lose their jobs and trapped millions more inside their homes without a foreseeable end date.
Thomas Lecocq, a seismologist at the Royal Observatory of Belgium, tells Nature that in Belgium, his team has observed a drop of about one-third after schools, restaurants and other gathering places closed and non-essential travel bans went into effect in mid-March.
In normal times, Lecocq tells Harmeet Kaur of CNN, readings from the Brussels station are "basically useless." The facility’s surface seismometer is now almost the equal of a detector buried in a borehole more than 300 feet underground that reliably picks up small quakes and quarry blasts.. “This is really getting quiet now in Belgium,” he says.
Most seismic stations are intentionally located away from cities to diminish potential interference—some are even hundreds of feet underground in deep boreholes to escape human din—but the Brussels station was established more than a century ago and the bustling city grew around it.
Lecocq shared the code he used for his analysis online and seismologists in other countries, including the United States, France and New Zealand, are now recording the effects of their own countries’ social-distancing measures on seismic activity, per the Atlantic.
On Twitter, Celeste Labedz, a graduate student in geophysics at the California Institute of Technology, also noted less noise picked up by a station in Los Angeles. “The drop is seriously wild,” she tells Nature.
Lecocq tells CNN that the graphs charting the diminished seismic noise show that people are staying home as many governments have instructed their citizens to do. "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,'" says Lecocq.
The inverse, detecting where activity is still high, could also be useful. As seismologist Raphael De Plaen of Universidad Nacional Autónoma de México, tells CNN, "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.'"