Scientists at the British Geological Survey (BGS) reported a change in the Earth’s seismic noise and vibrations amid the coronavirus lockdown. This change has been monitored through a space-based seismograph.

Ever heard of space-based monitoring of seismic activities?  This topic creates a scope for potential prelims question…

What is seismic noise?

• In geology, seismic noise refers to the relatively persistent vibration of the ground due to a multitude of causes.
• It is the unwanted component of signals recorded by a seismometer– the scientific instrument that records ground motions, such as those caused by earthquakes, volcanic eruptions, and explosions.
• This noise includes vibrations caused due to human activity, such as transport and manufacturing, and makes it difficult for scientists to study seismic data that is more valuable.
• Apart from geology, seismic noise is also studied in other fields such as oil exploration, hydrology, and earthquake engineering.

How are vibrations generated?

• We measure ground vibrations from earthquakes using seismometers.
• These are incredibly sensitive so they also pick up other sources of vibration too, including human activity, such as road traffic, machinery and even people walking past.
• All these things generate vibrations that propagate as seismic waves through the Earth.

Reasons for the decline

• Due to the enforcement of lockdown measures around the world to tackle the novel coronavirus pandemic, the Earth’s crust has shown reduced levels of vibration.

How do the reduced noise levels help scientists?

• The seismic noise vibrations caused by human activity are of high frequency (between 1-100 Hz), and travel through the Earth’s surface layers.
• Usually, to measure seismic activity accurately and reduce the effect of seismic noise, geologists place their detectors 100 metres below the Earth’s surface.
• However, since the lockdown, researchers were able to study natural vibrations even from surface readings, owing to lesser seismic noise.
• Due to lower noise levels, scientists are now hoping that they would be able to detect smaller earthquakes and tremors that had slipped past their instruments so far.

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