377 ISSN 0016-8521, Geotectonics, 2021, Vol. 55, No. 3, pp. 377–392. © Pleiades Publishing, Inc., 2021. Russian Text © The Author(s), 2021, published in Geotektonika, 2021, No. 3, pp. 78–95. Relationship between Strong Earthquakes and Activation of Deep Faults in Central Asia (Uzbekistan): Numerical Simulation of Stress Field Variations I. U. Atabekov a, *, T. U. Artikov a , R. S. Ibragimov a , T. L. Ibragimova a , and M. A. Mirzaev a a Mavlyanov Institute of Seismology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, 100028 Uzbekistan *e-mail: atabekovi@mail.ru Received October 5, 2020; revised April 11, 2021; accepted May 15, 2021 Abstract—The results of analyzing the data on strong М ≥ 5 earthquakes in Central Asia for 1901–2013 are presented. A statistical method for studying the influence of the strongest earthquakes in the region on the occurrence probability of seismic activation in a certain seismically active zone in Uzbekistan is used. Based on this method, the statistical significance of the difference between the fraction of strongest earthquakes in the region that fall within the alarm intervals of the studied seismically active zone and the fraction of cumu- lative time of alarms in this zone is assessed. It is established which seismically active zone in the Uzbekistan territory is most likely to manifest seismic activation if a strong earthquake occurs in the Central Asian region. A mathematical model is developed for the deformation of the Central Asia lithosphere, the lateral margins of which are being subjected to lateral compression. The proposed model is used to analyze changes in back- ground stresses in the crust of Central Asia caused by strong earthquakes in the territory bounded by the geo- graphical coordinates from 36° to 46° N and from 56° to 76° E. A numerical experiment is carried out by solv- ing the inverse problem of elasticity theory to determine the background stress in the lithosphere. By sequen- tially selecting the boundary stresses and varying the physical elasticity parameters, we have constructed the stages of crustal stresses conforming to their empirically known values. The earthquake source is simulated in kinematic dislocation with subdivision into types: a concentrated dipole with a moment (type I), a concen- trated double dipole without a moment (type II), and a singular volume. The numerical results of the model have shown that that the variations in stresses caused by a strong earthquake are largely determined by the proximity of orientation of displacement of the strong earthquake source and the axes of crustal structures affected by wave perturbation. In regions where stresses in the crust are close to critical, the stress increment can trigger seismic activation. Keywords: Central Asia, deep faults, numerical model, crustal stress, earthquake mechanism, seismicity acti- vation, correlation between activation periods DOI: 10.1134/S0016852121030031 INTRODUCTION The probability of strong earthquakes influencing the activation of seismicity of regions located a consid- erable distance from an earthquake source has been discussed by Russian and foreign geologists. Research- ers often give exact antipodes of opinions, from proven facts of a decrease in the earthquake preparation time caused even by small perturbations [14, 26] to emphatic rejection of such a probability. New impetus was given to studies due to the Landers earthquake with M = 7.3 that occurred on June 28, 1992 at 04:57 LT (the earth- quake epicenter was located near the city of Landers, California, USA), followed by seismic events recorded for 10 h at a distance of up to 1250 km from the epicen- ter; their origin was presumably related to the trigger effect of the earthquake [27]. The initiation of seismic- ity activation at the level of intermediate earthquakes in the Caucasus and Central Asia by deep-focal earth- quakes of the Pamir–Hindu Kush zone has studied [14]. Earthquakes with magnitudes М > 5 that occurred from 1961 to 1985 were analyzed based on data of International Seismological Centre [29]. Based on the processing of a large amount of statistical data, it is suggested that the process of earthquake preparation is not limited by the region of elastic energy accumula- tion and distant strong earthquakes sometimes exert a decisive influence at the final stage of source develop- ment. Based on a statistical analysis of strong earth- quakes from 1901 to 2005, it has been established that seismic activation at the level of earthquakes with М ≥ 5 for some seismically active zones in Uzbekistan mani- fests itself almost synchronously (±1 year) with the recurrence periods of strong earthquakes with М ≥ 7 in the Central Asian region [23]. In addition, a contrary opinion was stated in [12] based on the statistical analysis of earthquakes in