A quieter world during the lockdown

Humans are a really noisy species:hammering and digging,flying and driving,delivering heavy cargo all over the world.And those activities create noise as if it were from an earthquake,which masks delicate signals from faraway small earthquakes.

Raphael De Plaen,a seismologist（地震学家）at the National Autonomous University of Mexico,compares listening for small earthquakes during normal times to sitting at a wedding,at a table far away from the band.You can't really make out the music,because there are so many people laughing and talking in between you and the loudspeakers.

“And so now the lockdown is like coming during the rehearsal（排练）—no one is talking.So even though you're far away,the speakers are loud enough for you to listen to all the songs and clearly identify them.”

De Plaen says he and his team have been able to detect“songs”—in this case,signals from earthquakes which they didn't even know existed.And now that they've identified those signals,they'll be able to look back at decades of data and use these newly discovered seismic（地震引起的）fingerprints to better identify small earthquakes like these in the past.

The study,co-authored by more than 70 seismologists from around the world,appears in the journal Science.

In addition to discovering new seismic phenomena,the study also demonstrates how seismic data could be used to track human activity and movement—like traffic in a certain region,for example—all without the privacy concerns that go along with cellphone tracking.

“By definition,what we are observing is already anonymous（匿名的）—there's no way to actually know if someone like John Doe has left his home to spend the night in another place.”

De Plaen points out that this finding may be one of the only positive thing to come out of the global pandemic:the ability to better detect future earthquakes.

Reading Check

What might be one positive thing the lockdown of the pandemic brings according to Raphael De Plaen?

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