ИСТИНА

The differences in evolution of foreshocks and aftershocks sequences are analyzed. Foreshocks, the main shock of an earthquake, and aftershocks form a unique unity called a triad in [Guglielmi A.V. Foreshocks and aftershocks of strong earthquakes in the light of catastrophe theory // Physics-Uspekhi. 2015, V. 58. No. 4. P. 384–397]. At the same time, the magnitude of the main shock always exceeds the magnitudes of foreshocks and aftershocks. In the classical triad, the number of aftershocks is greater than the number of foreshocks. Sometimes foreshocks are not observed at all. In this case, it is natural to call the triad a shortened classical one. In the mirror triad, the number of foreshocks exceeds the number of aftershocks. Sometimes aftershocks are not observed at all. In this case, it is natural to call the triad a shortened mirror one. There are symmetric triads, for which number of aftershocks is equal to the number of foreshocks. Strong earthquakes (Grande Terremoto Solitario or - GTS), either before or after which there are no foreshocks and aftershocks, can also be attributed to symmetric triads. We used data on earthquakes that occurred on the Earth from 1973 to 2019 and were registered in the world catalog USGS/NEIC (https://earthquake.usgs.gov). The epoch superposition method were used. For all types of triads in different magnitude ranges of mainshock generalized sequences of foreshocks and aftershocks and their quantitative characteristics are given. Shown that the number of GTS is approximately equal to the number of classical triads. In the presence of foreshocks, the activity of aftershocks is higher than in the absence of foreshocks. The number of truncated triads significantly exceeds the number of complete ones. Observations results made it possible to hypothesize that the master equation for foreshocks evolution has the form of the differential equation with cubic nonlinearity. Shown that the waiting time for a strong earthquake (mainshock) follows the exponential distribution low and waiting time in sequences of foreshock and aftershock are well approximated by the power functions. This work was supported by the state assignment programs of the Institute of Physics of the Earth, Russian Academy of Sciences.