Block Structures and Kinematics of Eastern and Central Asia from GPS Data

摘要

The joint consideration of geological and geophysical characteristics and modern kinematics of blocks in eastern and central Asia allowed us to specify the previously suggested models of regional block structure; the degree of deformability of particular blocks; and the rates of displacement of blocks relative to one another and to the Eurasian Plate, assuming that its motion is described by the NNR-NUVEL-1A model. The data on velocities of present-day horizontal movements show that at least some blocks, e.g., the Southeast China and the Indochina-Sunda, behave in kinematic field as absolutely rigid bodies in terms of mechanics. The blocks that are localized near the modern subduction zones (the Okhotsk Block, the eastern part of the Japan-Korea Block) undergo intense deformation, and their displacement cannot be described by the model of absolutely rigid body motion on a sphere. In the region of the Eurasia-Hindustan collision, the velocities of modern horizontal movements appreciably differ from the velocities predicted by the NNR-NUVEL-1A model. Four areas have been outlined where modules of differences between real velocity vectors and velocity vectors predicted by the NNR-NUVEL-1A model linearly decrease with distance from border of the Indian Plate. Thereby, the rate of decrease is correlated with the intensity of seismic energy released in each area. The stresses arising between the large lithospheric plates are transmitted and relaxed within the transit zones at their boundaries.