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?1015 J, while along other boundaries it doesn’t exceed 3?1012-2?1015 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).
Highlights
Central Asia includes a territory situated between the Lake Baikal, Upper Enisei, Ob and Irtish in the north, east Kazakhstan, Tien Shan and the Pamirs in the west, southwest China and the Himalayas in the south, the middle course of the Yangtze, Hwang-Ho, and Amur rivers in the east (Figure 1)
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
1) The up-to-date geodynamics of central Asia is defined by the interaction of North Eurasian and Indian plates, which results in mosaic neotectonic structure of this territory
Summary
Central Asia includes a territory situated between the Lake Baikal, Upper Enisei, Ob and Irtish in the north, east Kazakhstan, Tien Shan and the Pamirs in the west, southwest China and the Himalayas in the south, the middle course of the Yangtze, Hwang-Ho, and Amur rivers in the east (Figure 1). In spite of that the majority of scientists traditionally included the whole territory of central Asia in the single Eurasian lithosphere plate It contradicts with the established block structure of the Eurasian lithosphere [1,2]. The bisector of its vertex nearly coincides with the GPS vector of the Indian Plate (Figure 2) Some years ago it was shown on the basis of seismicity, active faults and GPS data that only the northern part of the Eurasian Plate should be regarded as an independent and relatively indivisible lithosphere unit, which was named the North Eurasian Plate [8,9,10]. Each of zones consists of numerous blocks, the independent existence of which is proved by the widespread development of active faults ascertaining geodynamic heterogeneity of central Asia (Figure 3). In our paper we’ll try to establish the connection of the intensive seismicity with the block structure and geokinematics
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