Earth vibrating less due to lockdowns

Coronavirus pandemic causes ‘quiet period’ for seismic noise Study

Coronavirus pandemic causes ‘quiet period’ for seismic noise Study

Researchers suggest the anthropause could help scientists develop new techniques for filtering out human-caused seismic noise and honing in on the kinds of seismic signals that might precede a natural disaster, like an quake, landslide or volcanic eruption.

More broadly, the seismic lockdown will help us to differentiate between human and natural causes of seismic noise.

Vibrations travel through the earth like waves, creating seismic noise from earthquakes, volcanoes, wind and rivers as well as human actions such as travel and industry.

Seismic activity doesn " t just come from earthquakes, volcanoes and landslides.

Although 2020 has not seen a reduction in earthquakes, the drop in human-caused seismic noise is unprecedented. The study shows that the strongest seismic noise reductions were found in urban areas, but the authors also noticed the lockdown signatures on sensors buried hundreds of meters into the ground and in more remote areas, such as in Sub-Saharan Africa.

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.

Seismometers have long recognised a drop in this higher-frequency shaking at nights, at weekends and throughout getaway intervals - but this lull was much additional pronounced and extended.

Study co-author Dr Stephen Hicks, from Imperial's department of earth science and engineering, said: "This is the first global study of the impact of the coronavirus anthropause on the solid Earth beneath our feet".

During the study, the researchers collected and analyzed seismic data from 268 seismic stations spread across 117 countries from all over the world.

The greatest reductions were found in cities such as Singapore or NY , but were also observed drops in seismic noise in the remote areas like the Black Forest of Germany or of Rundu, in Namibia .

We found that seismic noise dropped by an average of 50% in 77 countries between March and May 2020. This coincided with flight data, according to which tourists were returning home several weeks before the official closure.

Seismologists Dr Jessica Irving and Dr Anna Horleston, from Bristol's School of Earth Sciences, were involved in the research, working with data from North America, the United Kingdom and Africa.

"Earthquake signals can often be concealed or obscured by seismic noise, but they appeared much more clearly on the seismometers during lockdown. It also reminds us of the wide range of applications which use modern-day geophysics".

Seismic noise has risen for decades as populations and economies have grown.

The changes have also given us the opportunity to listen in to the Earth's natural vibrations without the distortions of human input.

Previously concealed quake signals have been heard for the first time, and researchers say the lockdown quietening could open up new fields of research that improves detection of forthcoming natural disasters. This correlation allows open seismic data to be used as a broad proxy for tracking human activity in near-real-time, and to understand the effects of pandemic lockdowns and recoveries without impinging on potential privacy issues.

The own Lecoq says, "with increasing urbanization and the growth of populations around the world, more and more people will live in areas geologically hazardous". Therefore, it is becoming more important than ever to distinguish between natural and man-made noise so that we can "listen" and better track the movement of the ground under our feet. The study cited places ranging from Boston to Barbados, the Namibia-Angola border, Germany's Black Forest, and the uninhabited island of Motutapu off Auckland, New Zealand.

The hush - part of a global pandemic-induced reduction in human effects on the world dubbed by some as the anthropause - is, seismologists say, a scientific gift, for two main reasons. This research can help start a new area of study.

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