Findings from a new study suggest that human-induced seismic noise has been reduced as a result of COVID-19 measures.
The research which was published on July 23, 2020 in Science, suggests that the human activity that causes seismic noise was decreased by up to 50%, a fact that enabled scientists to better understand the differences between natural and human-induced earth vibrations.
Seismic noise is practically considered the redundant data that seismometers detect due to persistent vibrations of the ground. The signals mainly consist of low and high frequency elastic surface waves and a small number of body waves (Primary and Secondary waves). The sources of seismic noise can be caused by human activity (e.g. transportation and industry) or by natural processes such as winds, river and ocean waves, volcanoes or other earth’s procedures.
The seismic noise associated with human activities has significantly changed during the past decades due to developments in technology. The reduction in seismic noise was a result of the measures taken against the coronavirus spread that included the extensive lockdowns, the business closures and the restrictions of traveling.
Temporary alterations in human-induced vibrations are common throughout the year (e.g. during Christmas or Easter when people are on vacations and stay more at home). These short drops in seismic activity are also known as “anthropauses”. However, the duration and the size of the current reduction is unprecedented.
The research team conducted a detailed investigation on data from 268 seismic stations established in 117 countries. They deduced that the noise reduction pattern was similar to the enforcement of the restrictions measures to tackle the COVID-19. In particular, the human-induced seismic noise dropped in China in January 2020 and in the rest of the world from March to April 2020. The highest percentage decrease was observed in populous areas such as big cities.
According to the research team, the current decrease provides a great opportunity to evaluate the impact of natural processes on earth’s vibrations and figure out a way to distinguish them from human-induced noise. If this is achieved, the impact of natural processes and their potential risk to human infrastructure may be better understood. “…(It is) 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. This study could help to kick-start this new field…,” Dr. Thomas Lecocq, the lead author of the study and a seismologist at the Royal Observatory of Belgium, stated.
The study suggests that this period is also beneficial in terms of detecting an actual (small-scale) earthquake which would be a difficult task before due to the seismic noise. Therefore, researchers are optimistic that even smaller earthquakes can be detected for as long as this situation continues.
Click the video in Media section below to watch the seismic noise changes before and after the COVID-19 lockdowns.
Source: Imperial College London
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