Scientists can record tiny earthquakes with silent lock


For seismic scientists, having hundreds of millions of people on the streets and in the skies provides a wealth of data on the planet.

All of these planes, trains and automobiles that do not operate due to home stay policies designed to combat the spread of COVID-19 have reduced noise pollution in some cities by more than half, allowing seismologists to record sounds. from inside the Earth that they never could before.

John Cassidy, seismologist and seismologist at Natural Resources Canada, says that vacations like Christmas are closest to these low levels of background noise and only for one day at a time.

“It is truly unprecedented to see this level of calm,” said Cassidy, who is also an adjunct professor at the University of Victoria.

Cassidy said that things had changed so quickly in terms of locking, few people had thought much about the impact on noise until a scientist in Europe noticed it and the news started to spread quickly in the community.

A functional seismograph is featured in an earthquake exhibit at the Discovery Cube Science Center in Santa Ana, California in 2018. For each earthquake of magnitude 2.0, which can be strong enough to swing the trees or cause a small ripple on the surface of a lake, Canada will experience 10 earthquakes of magnitude 1.0, which will only be felt below the surface. (Mike Blake / Reuters)

In Canada, during the third week of March, major cities began to see traffic almost disappear, with normally crowded highways, sometimes entirely devoid of cars. As international flights have been canceled and domestic travel has slowed, air traffic has also decreased significantly. Many large manufacturing plants have also reduced their hours of work or closed completely during the lockout.

Many seismology stations in Canada are not deliberately in large cities, in order to reduce noise pollution at all times. But for those who are, like in Montreal and Ottawa, the drop in noise after the blockages began in mid-March was immediately noticeable.

Up to 60% noise reduction

In Montreal, noise fell by more than 40%, in Ottawa by 33% and in Calgary, the drop was more than 60%. In Victoria, where the station is located far from high-traffic areas, the drop in noise was slightly lower, at almost 19%.

In large cities that are considered high-risk seismic zones, such as Los Angeles, the data is particularly useful.

Road traffic sets up in Calgary, Alberta on Wednesday, February 8, 2017. Reduced traffic due to COVID-19 blockages has reduced noise by more than 60% in Calgary, according to seismic researchers. (Jeff McIntosh / The Canadian Press)

Cassidy says that without seismographs picking up all the noise generated by humans, scientists are recording small earthquakes around the world that normally go unnoticed.

Canada normally experiences between 4,000 and 5,000 earthquakes a year, most of them small-scale and not felt by people. Cassidy said that for every 2.0 magnitude earthquake, which can be strong enough to swing trees or cause a small ripple on the surface of a lake, Canada will experience 10 earthquakes of magnitude 1.0, which are only felt below the surface and noticed by the seismology equipment.

And for each 1.0 earthquake, there are 100 of magnitude zero. It is these zero magnitude earthquakes, or some that are even smaller, that are now detected.

The additional information is useful for everything from monitoring active volcanoes to better defining fault zones and even developing better images of the Earth’s structure.

Cassidy says it won’t help predict future big earthquakes yet, but will be helpful in helping engineers create better building codes for earthquake prone areas.

Cassidy said that knowing it was going to be temporary, seismologists are working hard to track the data while they can get it.

“It’s an unusual time,” he said.


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