The empty Via Simon Bolivar or Transistmica Highway, in Panama City, on May 31, 2020, the last day of total lockdown. Photo: Luis Acosta/AFP via Getty Images
During lockdowns and other measures to control the spread of the novel coronavirus there was as much as a 50% drop globally in the seismic vibrations humans normally generate, according to new research.
Why it matters: Human seismic noise can drown out signals from earthquakes, volcanic eruptions and other geological hazards and natural sources. The "quiet period" of 2020 may help to improve warning systems by offering an opportunity to separate natural sounds from those generated by human activity.
Driving, drilling, walking, flying and other human activities vibrate the Earth's surface, creating seismic noise.
What they found: Using data from 268 seismic stations in 117 countries, researchers measured the effects of lockdowns on high-Frequency (4–14 Hz) Seismic Ambient Noise (hiFSAN), which corresponds to vibrations typically generated by human activities.
- They observed the effects of lockdowns at 185 stations and found a "near-global reduction in noise, commencing in China in late Jan 2020, then followed by Europe and the rest of the world" from March to April 2020.
- The noise level reduction lasted longer and was at times quieter than the Christmas to New Years period, Thomas Lecocq, a seismologist at the Royal Observatory of Belgium, and his colleagues from around the world report Thursday in the journal Science.
- The drops were more pronounced in more-populated areas (New York and Sri Lanka), but were observed in less-populated regions (for example, Germany's Black Forest) as well.
The big picture: "This is the first time to our knowledge that this kind of effect is visible on such a widespread area — the whole globe — and for such a long time period," says Lecocq.