Seismic Noise | 17 Apr 2020
Why in News
Scientists at the British Geological Survey (BGS) have reported a change in the Earth’s seismic noise and vibrations amid the coronavirus lockdown.
- These findings have come two weeks after seismologists at the Royal Observatory in Belgium observed a 30-50% fall in levels of seismic noise since schools and businesses were closed in mid-March.
Key Points
- Seismic noise
- In geology (study of rocks), seismic noise refers to the relatively persistent vibration of the ground due to a multitude of causes.
- This noise includes vibrations caused due to human activity, such as transport and manufacturing.
- Scientists first observed this seismic noise — everything recorded on seismograms that cannot be attributed to earthquakes — at the end of the 19th century.
- It is the unwanted component of signals recorded by a seismometer 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.
- Benefits of reduction in seismic noise
- Usually, to measure seismic activity accurately and reduce the effect of seismic noise, geologists place their detectors 100 metres below the Earth’s surface.
- Because, the seismic noise vibrations caused by human activity are of high frequency (between 1-100 Hz), and travel through the Earth’s surface layers.
- 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 tremors that had slipped past their instruments so far.
- Usually, to measure seismic activity accurately and reduce the effect of seismic noise, geologists place their detectors 100 metres below the Earth’s surface.
Seismometer
- Seismometer is the scientific instrument that records ground motions, such as those caused by earthquakes, volcanic eruptions, and explosions.
- 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.