Weekly Current Affairs: April week-3 - Earth’s seismic noise

In a latest development, scientists at the British Geological Survey (BGS) have reported a change in the Earth’s seismic noise and vibrations amid the coronavirus lockdown.

• 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.
  • Seismometer is 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.

Why seismic noise levels are reducing now?

• As per the Belgian study, 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.
• The scientists measured 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.
• The scientists then compared the average daytime noise levels at seismic stations in the UK in the two week period since the start of the Covid-19 lockdown with the average noise levels for the beginning of the year.
• The results show reductions in noise levels at most of stations of between 10-50%."

Are these restrictions helpful?

• 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 have said that they 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 also see low amplitude parts of the ground motions caused by larger earthquakes that had slipped past their instruments so far.
• Moreover, the fall in noise will also profit seismologists who utilize generally happening history vibrations, such as those from crashing sea waves, to probe Planet’s crust.

A fall in human-induced sound could enhance the degree of level of sensitivity of detectors to natural waves at comparable frequencies. There’s a substantial possibility definitely it could bring about much better measurements.