Seismic Noises

WHAT IS SEISMIC NOISE? 

Seismic noise alludes to vibrations within Earth’s crust and is set off by natural as well as man-made marvels like tremors, volcanoes, bombs, etc. Ordinary human activity- for example, vehicular traffic, manufacturing processes in industries, construction work, planes thundering overhead, or simply people strolling down the road also produce seismic noise, which is recorded as a near-ceaseless signal on seismometers. These signals created by individuals are usually referred to as anthropogenic seismic noise.

Seismic noise practically acts like a foundation sound for seismologists, meaning it is the undesirable background part of the signal recorded by the seismometer. But with human movement at a minimum due to the global pandemic, anthropogenic seismic noise has been hushed to a large degree.

IMPACT OF GLOBAL PANDEMIC ON SEISMIC NOISE

The current global pandemic has carried the world to a crashing halt and induced a ‘wave of silence’ as high-frequency commotion generated by factories, traffic, and other human exercises fell sharply during a period set apart by the lockdowns and public isolation. A group of seismologists from universities around the globe, including the Imperial College of London and the Royal Observatory of Belgium, contemplated the effects of the pandemic on noise-levels worldwide and found that high-frequency commotion brought about by human activities dropped by around 50% during the summer this year.

“This quiet period is the longest and largest dampening of human-caused seismic noise since we started monitoring the Earth in detail using vast monitoring networks of seismometers”, explains the co-author of the study, Dr. Stephen Hicks from the Imperial College of London.

While the tremors are as yet occurring, the drops in anthropogenic seismic noise, particularly in urban regions, are uncommon. It is substantially more than tranquil periods seen at the weekends, festivities, and even during late evenings. Few researchers have portrayed this time of noticeable worldwide anthropogenic seismic noise decrease as ‘anthropause’. The ‘anthropause’ has likewise permitted researchers to get more precise estimations of seismic waves, which can thus assist them with differentiating between human and natural seismic clamor more clearly.

“With increasing urbanization and growing global population, more people will be living in geologically hazardous areas. It will, therefore, become more important than ever to differentiate between natural and human-caused noise so that we can ‘listen in’ and better monitor the ground movements beneath our feet”, says the lead author of the study, Dr. Thomas Lecocq from the Royal Observatory of Belgium.

WHY ARE THESE PHENOMENA IMPORTANT? 

Due to this, researchers state that they will have the option to spot more vulnerable signals, which were generally concealed by the commotion created by human movement. This implies that researchers will have a better shot at observing an entire scope of seismic behavior, including the smallest quakes or the early indications of volcanic eruptions. This will additionally help by making seismic hazard assessment more accurate. The investigation states- ’Low noise levels during the lockdowns could, therefore, permit detection of signals from new sources in regions with inadequate seismic indexes.’

After the lockdown was imposed in Mexico, a low recurrence seismic tremor at 15 km depth was detected south-west of Petatlan. As per the researchers, it would have been profoundly impossible for the tremor to have been registered outside of Mexico’s urban surroundings before the pandemic effect. 

This research combined with the phenomena of ‘anthropause’ will help researchers to analyze the activity of our planet and have a detailed understanding of the fault lines and tectonic plates, it may even lead to research to build better 3D predictive models which could inform us about high-alert areas well before time.“It’s important to see those small signals because it tells you if a geological fault, for example, is releasing its stress in lots of small earthquakes or if it is silent and the stress is building up over the longer term”, Dr. Hicks tells The Guardian.

“This study could help to kick-start this new field of study.” The study’s authors hope that this work will inspire future research on the seismic noise.“The lockdowns caused by the coronavirus pandemic may have given us a glimmer of insight into how human and natural noise interact within the Earth. We hope this insight will spawn new studies that help us listen better to the Earth and understand natural signals we would otherwise have missed”, states Dr. Hicks.

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