Up-To-Date Geodynamics and Seismicity of Central Asia

Abstract

The analysis of the seismicity in central Asia shows its distribution within a "triangle" of maximal inner-continental seismic activity, which is situated between south edge of the Lake Baikal and the Himalayas. The "triangle" coincides with the central Asian transit zone which divides the north Eurasian and Indian lithosphere plates and provides transfer and relaxation of tectonic stresses that arise between them. The central Asian transit zone consists of numerous crust blocks of different sizes. Blocks' boundaries are often represented by not only single faults but relatively wide interblock zones characterized by intensive shattering of rocks and releasing a significant quantity of the seismic energy. The most active interblock zones limited the Pamirs, Tien Shan, Shan, and Bayanhar blocks as well as north boundaries of the Indian Plate. The quantity of the seismic energy releasing along each of them reaches ≥ 5 × 10 15 J, while along other boundaries it doesn't exceed 3 × 10 12 -2 × 10 15 J. The majority of the most intensive seismic events took place just in these interblock zones. The total quantity of seismic energy is generally diminished away from the boundary of the Indian Plate, but sometimes the maximal quantity releases in inner parts of the transit zone at the distance 500-1500 km from the plate boundary. The most active interblock zones of central Asia differ from subduction and collision zones by depth of their penetration in lithosphere and at the same time are rather near to them by the volume of energy realizing. The examination of interblock zones shows that the majority of intensives earthquakes occur within them in regions with sharp changes of geodynamic conditions. On the whole the most part of central Asia is situated under the influence of the Indian indenter, which causes the prevailing of transpression tectonics. An abnormal high seismic energy releasing depends of deep continuation of the plate slab in collision zones (Pamirs, Himalayas), intensive displacements along strike-slips and thrusts due to collision processes and deep lithosphere unhomogeneity (Tien Shan, Bayanhar), as well as of sharp changes of geodynamic conditions because of influence of plate movement and supposed mantle plumes (north Mongolia, the Baikal region).

Seismic-Geodynamic Monitoring of Main Electric Power-Stations in East Europe and North Asia

“…The intensity of releasing energy quickly increases to south in the region from 1 × 10 −6 J -1 × 10 −5 J up to 1 × 10 12 J -1 × 10 14 J. High seismic zones with M 7.0 -7.9 and more coincide with active faults in the boundaries between the north Eurasian Plate and Iran, Afghan, Pamir, Tien Shan blocks as well as in the boundaries between some blocks inside the central Asian transit zone [5]. HES near Alma-Ata, Tashkent and Dushanbe lie in these zones.…”

“…After GPS data the south part of the north Eurasian Plate moves east-northeast with the azimuth 75 -83 NE, while the majority blocks south of it displace with azimuth 50 -60 NE. The difference in horizontal moving direction results in the thrusts predominance in the south boundary of the plate [5]. Velocities of horizontal displacements change from 26 mm/y to 30 mm/y and a vertical upwarping in main mountain ranges occurs with velocities 0.5 -2.0 mm/y.…”

“…As it was established earlier [2] most parts of east Europe and north Asia belongs to a large north Eurasian lithosphere plate, which boundaries are: the Gakkel Ridge and seismoactive faults in the Chersky Range, zones of active faults in south Verchoyanie, Stanovoi Range, the Baikal Rift, Altai -Sayany Region and Tien Shan, the Pamirs Syntax, fault zones of the Kopetdag, Caucasus, the region west of the Black Sea, the Carpathians and Alps. A blocks framework of the plate was characterized in detail in some papers [3][4][5], in which transit zones were distinguished on its boundaries with neighboring lithosphere plates. The zones contain a number of crustal blocks and represent areas of the transfer and relaxation of the tectonic energy arising in the result of main plates' interaction.…”

The 102–103° E geodivider in the modern lithosphere structure of Сentral Asia

“…The former is located between North-Eurasian and Indian plates and characterized by the transpression regime with predomination thrusts and slips. The latter is located between the North Eurasian and Pacific plates and dominated by the transtension regime with extension structures [Gatinsky et al, 2011]. Our detail study of the geodivider and adjacent parts of transitional zones aimed at providing a fresh approach to interpreting the current regional geodynamics, the relations between the surface structures, their kinema-tics and the deep anomalies, as well as clarifying the main causes of different regimes at the geodivider sides.…”

Evolution of Rotation Structures in the Earth’s Geological History

“…The examination of interblock zones shows that the majority of intensive earthquakes occur within them in regions with sharp changes in geodynamic conditions. As a whole, most of Central Asia is influenced by the Indian indenter, which is responsible for the prevalence of transpression tectonics" (Gatinsky et al, 2011 Table 2. Geographic coordinates of GPS stations (in the east system) and their linear velocity vectors in the Tibet Plateau and its environs, based on the data of (Yuping et al, 2004;Zemtsov, 2007Zemtsov, , 2009a The estimates of ARV vectors ω, obtained for various Eurasian domains in (Zemtsov, 2006(Zemtsov, , 2007(Zemtsov, , 2009a, show that the ω modulus varies several times (see Fig.…”