关键词: 大陆强震, 有限元模拟, 黏弹性, 动力学

Abstract: Based on the analyses of the density of energy released by strong earthquakes in East Asia, the contemporary dynamics of continental deformation is studied. The west China and its vicinity including North China can be considered as the Continental Meizoseismal Region of China. The deformation and stress fields in China and its vicinity are studied by modeling the long-term squeezing of the Indian subcontinent in term of 3-dimensional layered visco-elastic finite element method. The regime of energy distribution in this region is basically similar to the model with Indian's indentation, but has some differences. The super shear zones on both sides of the Tibet Plateau proposed by Dewey et al. (1990) are essentially the deformation twist belts: the stress is concentrated in both belts as compared with that inside and outside the plateau, in spite of a slight difference of stress orientations from the elastic homogeneous model. The vectors of crust motion in east China are leaning towards the east, and the vectors in the east and northeast parts of the Tibet Plateau are significantly different from those in their vicinity. There are three arcuate belts with high seismic energy densities in the eastern Tibet Plateau: Chayu arc in the southeast, Kangding arc in the northeast and Haiyuan arc in the north-northeast. The meisoseismal region in China is developed by three combined dynamic processes: (1) The long-distance squeezing of the Indian subcontinent results in the gradual extending of the deformation starting from both corners of the plateau and ending in the collision zone, which then causes the formation of the deformation twist belts on both sides of the plateau. The thick crust of the Tibet Plateau provides the medium condition for elastic energy accumulation. The creep of the lower crust at higher temperature leads to the concentration of stress in the upper elastic layer. (2) The large-scale eastward motion of the eastern Asia has given rise to the change of the squeezing direction of Indian Plate in the northern Tibet from north-northeast to northeast, and the turning of both the deformation twist belts from north-northeast-trending to northeast-trending. (3) The inhomogeneous extrusion within the Tibet Plateau promotes the formation of three arcuate belts on the eastern side of the Tibet Plateau.

Key words: continental strong earthquake, finite element method analysis, visco-elasticity, dynamics