Seismotectonics of Central and Southern Uzbekistan and Seismic Hazard Assessment of Its Territory

The seismotectonic position of the territory of Central and Southern Uzbekistan is analyzed. It is shown that the territory is characterized by a layered-block structure. Four large blocks of the Earth’s crust are distinguished. Two blocks belong to the Turan microplate, while the remaining blocks belong to the Western Tien Shan and Afghan–Tajik microplates. Positive and negative morphostructures of each geodynamic block are described. Active crustal faults in three different directions are distinguished. In the central part of Uzbekistan, the most active are faults with a northwest strike. These faults are characterized by a long history of development, complex internal structure, and high amplitudes of neotectonic movements. Fault troughs are confined to such faults. Newly emerged faults with a northeast direction complicated the structure of large regional structures. If within Central Uzbekistan these faults were of secondary importance in the formation of the modern deformation structure of the earth’s crust in the study region, then in the territory of Southern Uzbekistan faults of this direction are the main ones and control modern seismicity. A probabilistic analysis of the seismic hazard of the territory of Central and Southern Uzbekistan is carried out. Three types of calculation models of seismic vibrations sources are considered: quasi-homogeneous seismological provinces, active crustal faults and seismogenic zones. Parameterization of seismic source models is carried out, including the determination of seismic potential, recurrence parameters of earthquakes of various magnitudes, the predominant kinematic type of slip in the foci of earthquakes of each source. The seismic impacts are calculated using several attenuation dependences developed for the Central Asian region. The weights for the attenuation dependences are selected based on the ranking procedure according to the degree of applicability to the study area. The seismic hazard in the engineering parameters of seismic vibrations was was assessed. Taking into account the recurrence periods of seismic impacts, probabilistic maps of detailed seismic zoning of the territory of Central and Southern Uzbekistan were developed.