Researchers at the British Geological Survey (BGS) have noticed something interesting happening with the Earth’s vibrations during the COVID-19 lockdown. About two weeks after seismologists in Belgium observed a 30-50% decrease in seismic noise when schools and businesses closed in mid-March, the BGS scientists also found a change in the Earth’s seismic activity. It’s like the planet itself is responding to the changes in human activity caused by the lockdown.
What is Seismic Noise?
- When the Earth shakes due to things like earthquakes, volcanoes, or even explosions, it creates what we call seismic noise.
- Seismometers, which are special devices that record ground movements, pick up not only these natural events but also something called seismic noise.
- Believe it or not, our everyday activities contribute to this seismic noise. Things like cars on the road, machines in factories, the noise from airplanes, or just people walking around town all add to it.
- The noises we humans make are specifically called anthropogenic seismic noise.
- For seismologists, this seismic noise is like background noise – it’s the part of the signals recorded by a seismometer that they don’t really want, but have to deal with.
Why is this important to record this noise?
- Scientists can now detect fainter signals, helping them better understand geological faults and improve seismic hazard assessments.
- Small signals provide valuable insights into seismic activity, allowing scientists to monitor a wide range of behaviors, from the tiniest earthquakes to early indications of a volcanic eruption.
- This advancement gives scientists a more accurate and improved chance at keeping a close eye on potential geological events.
Benefits
- Scientists usually put their earthquake detectors about 100 meters underground to accurately measure seismic activity. This is because the vibrations caused by human activities, known as seismic noise, are at a high frequency (between 1-100 Hz) and can travel through the Earth’s surface layers.
- During the lockdown, researchers discovered that they could study natural vibrations even by placing detectors on the Earth’s surface. This was possible because there was less human activity causing seismic noise.
- With lower levels of noise, scientists are optimistic that they can now detect smaller earthquakes and tremors that were previously missed by their instruments. The reduced interference allows for a more precise understanding of Earth’s natural seismic activity.
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