Seismometers Worldwide Detect Decrease in Human Activity Amid Coronavirus Lockdowns

The Lincoln Memorial square in Washington DC will be empty on March 17, 2020.

The square in front of the Lincoln Memorial in Washington D.C. is empty on March 17, 2020.
Photo: Win McNamee (Getty Images)

Seismometers around the world are recording the decreased seismic activity due to people staying at home amid covid-19 social distance regulations.

These detectors measure seismic waves Earth’s crust, but they also pick up humans movement, industry and traffic in the form of higher frequency noise patterns. Amid those who stayed at home, the Royal Observatory of the Belgian geologist and seismologist Thomas Lecocq decided to look at the seismometer of the Royal Observatory and noted that the noise level in Brussels was more like a winter holiday than a working day. Other seismologists have found a similar noise reduction in their local seismometers.

The surface station of the Royal Observatory of Belgium was once in a suburb, Lecocq told Gizmodo. But the city is extensive and the measurements of the seismometers now reflect the vibrant human activity in the city. “When it snows it is quiet and when there is a marathon, we can see people running, ”he said.

A seismometer reading in Belgium in the past year, showing a decrease in human-made seismic noise in the past two weeks. The green line indicates medium noise. The levels approach those during the winter holidays.

A seismometer reading in Belgium in the past year, showing a decrease in human-made seismic noise in the past two weeks. The green line indicates medium noise. The levels approach those during the winter holidays.
Graphic: Thomas Lecocq

Lecocq studies subtle changes in seismic sound. There are not many earthquakes in Belgium, but by characterizing the sound they can figure out how to remove it to see weaker or more distant events. In addition, humans are not the only ones producing seismic noise; the wind and the ocean do the same, and seismologists can use this sound to monitor and image Earth’s crust. So it only made sense that he looked at the impact of it the persistent Covid-19 pandemic. The Royal Observatory of Belgium placed the graph showing the reduced seismic noise on social media.

The measurements made sense to Susan Hough, a USGS seismologist. “If almost everyone stayed at home and didn’t move a muscle, daytime noise levels would approach normal nighttime levels,” she told Gizmodo in an email.

Other seismologists have conducted analyzes on seismometers elsewhere. The United Kingdom registered one decrease in noise from a station along a highway, while stations are in France and New Zealand have also detected the quieter seismic environment while people stay at home. Lecocq wrote a tutorial for those interested in looking at other seismic stations.

These charts are little more than scientific curiosity, but the temporary decrease in noise can be useful for seismologists, because they can get more information from their seismic data, Lecocq told Gizmodo. These seismometers now have a better sensitivity to the higher onesfrequency events whose signature is otherwise clouded by human activity, such as wind and groundwater behavior. Nthere is not only less seismic noise, but also less audible noise; Lecocq envisioned a study that correlates audible noise with seismic noise and even study how audible noise has increased in cities using seismological data.

These measurements serve as a clear reminder of the ongoing pandemic and of the many ways in which human behavior effects the planet.

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