Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc., geographical features and their location- changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.
What is earth’s seismic noise?
What to study?
For Prelims and Mains: Seismic noise- meaning, source, features and effects.
Context: Scientists at the British Geological Survey (BGS) have reported a change in the Earth’s seismic noise and vibrations amid the coronavirus lockdown.
- They have observed a 30-50 per cent fall in levels of ambient seismic noise since schools and businesses were closed in mid-March.
- Seismologists around the world have now begun a collaborative effort to study the fall in seismic noise levels.
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 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 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.
- What are seismic waves?
- Difference between seismic waves and noise?
- Difference between body waves and surface waves?
- What is magnitude scale and intensity scale? How are they measured?
- Most destructive seismic waves.
What are seismic noises? How lockdown has brought down these noise levels? Discuss.
Sources: Indian Express.