Imagine being able to talk directly with the earth – what would you say? What if the earth was able to answer all the questions that you ask rhetorically when you sit cosy by the window, watching raindrops and contemplating the earth’s deepest secrets? Imagine if all the environmental queries that come to your mind when you lie in the fields of barley, admiring sun rays reflected from the mirrored sky, could now be answered. The earth is now found to be speaking louder than humans. Your questions may be heard.

A dramatic quietening of the world, caused by social distancing measures, closure of services, and drops in travel due to the ongoing global pandemic has finally allowed the earth to take a deep breath and speak.

A study, published in the journal Science on Thursday, was conducted using international seismometer networks. Scientists found that the lack of global human activity has shown the most prolonged and pronounced reduction, roughly 50%, in human-linked seismic vibrations ever recorded. 

The findings highlight the importance of the scientists’ ability to hear the earth’s natural signals. It shows that scientists can detect subtle signals from subsurface seismic sources that would have been concealed in noisier times. It also says that scientists can now detect earthquakes and tremors in Europe and countries further afield than their equipment usually allows.

“Our study uniquely highlights just how much human activities impact the solid Earth, and could let us see more clearly than ever what differentiates human and natural noise,” said Dr Stephen Hicks from the Department of Earth Science and Engineering.

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Vibrations like waves

The study, co-led by the Royal Observatory of Belgium and five other institutions around the world, was conducted using data from 268 monitoring stations in 117 countries. A team of international researchers used devices, known as seismometers, to measure the noise caused by vibrations within the earth.

Seismometers are sensitive scientific instruments used to record vibrations travelling through the ground – known as seismic waves. High-frequency vibrations contaminate seismic records from natural sources. According to Dr Stephen Hicks, the “buzz” comes either from humans, walking around, doing industrial work, driving cars, or wind, waves, rivers, and earthquakes at the surface.

Hope, future, and pollution

Over the past few decades, seismic noise has gradually increased as economies and populations have grown. The drastic changes to daily life have provided a unique opportunity to study the environmental impacts, reductions in emissions and pollution in the atmosphere. 

As 2020 has shown positive results on the environment, from a drop in air pollution to now a decline in human-included vibrations, there is hope for a noise-free and pollution-free future. It also provides hope for further research to be developed to listen to the earth more deeply.

Will the 2020 seismic noise quiet period allow new types of signals to be detected from the earth? According to the study, the first evidence that previously concealed earthquake signals, especially during the daytime, already appeared much clearer on seismic sensors in urban areas. The study’s authors hope that their work will lead to further research on the seismic lockdown. 

As urbanisation continues, it will be significant to characterise the anthropogenic noise that humans cause, so that seismologists can better listen to the earth. Finding previously hidden signals from earthquakes and volcanoes will be a crucial aim for scientists. Speaking with the planet and uncovering its other signals will be another aim for every one of us.

Berta Balsyte
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