Pandemic Seismology

2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24

The pandemic of coronavirus infection and global quarantine have led not only to purification of the atmosphere, but also to geophysical consequences: seismologists around the world record a sharp decrease in the level of anthropogenic microseismic noise. We asked Russian seismologists exactly how the pandemic affected the Moscow geophysical environment.

There are no earthquakes in central Russia, and notable seismic events in Moscow are echoes of powerful earthquakes in other regions. In the capital, for example, they felt the Carpathian earthquake in March 1977 with a magnitude of 7, 4 and the Sea of Okhotsk earthquake in May 2013, whose magnitude reached 8, 3. In both cases, shocks were felt mainly on the upper floors of buildings, where the intensity of vibrations did not exceed 2-3 points. But this does not mean that the seismic stations do not hear anything the rest of the time - they constantly record high-frequency seismic noises. Their sources are wind, waves in the ocean, and in addition, human activities: trains, subways, cars, airplanes, factories and power plants.

Since the beginning of the "Moscow isolation", the Moscow seismic station has felt a sharp decrease in the level of microseismic noise, said Ruslan Diaghilev N + 1, deputy director for scientific work of the Unified Geophysical Service of the Russian Academy of Sciences.

The illustration below shows the averaged power spectra of microseismic noise according to the data of the seismic station "Moscow". The level was calculated for three time intervals with a duration of two days. The first interval is Thursday and Friday of the last working week, the second interval is weekends, the third is Monday and Tuesday of the current week, when Muscovites were at home in quarantine or self-isolation.

“Usually man-made noise is most strongly represented in the frequency band above 1 hertz. We did not show the frequencies below, as they are mostly natural. The graph shows that in the first days of the new week, microseismic noises remained at the weekend level, and in the 14-16 hertz band they became even lower. The decrease in the level in terms of frequencies is uneven. In the lower band - about two times, at high frequencies the difference reaches four to five times,”explains Diaghilev.

If the fluctuations in the Moscow seismic noise level are presented in the form of a chronological sequence, then we get the following graph:

Here, the level of the amplitude of the noise is measured in the speed of seismic vibrations. It is clearly seen that it decreased during the previous weekend, but did not return to the level of normal working days: Monday and Tuesday turned out to be "seismic weekends".

Seismic calm is also recorded by Belgian seismologists. According to them, the seismic situation has become quieter by 30-50 percent, which roughly corresponds to the level of the Christmas holidays.