关键词: 垂直运动, 三维有限单元, 构造应力场　剪应力增量

Abstract: Based on the seismic and geologic information available, North Qilian and Hexi Corridor area is divided into a number of 3-D finite elements. On the assumption of linear elastic model, the general tendency of vertical deformation spanning about 20 years in this area is simulated. The simulated results of this area bear a close relation with boundary condition and variation of background stress field. Among them, the result obtained by taking the increment of tectonic stress field as loading condition and stable block as displacement boundary condition, is in good consistence with the general distribution of vertical deformation in this area in the past 20 years. Based on this acknowledgement, the increment of the background stress field is estimated. The pressure change along N-S direction is +0.11MPa, and that along E-W direction is +0.04MPa (compressive pressure is positive). The quantity of the pressure change along E-W direction is three times of that along N-S direction. In addition, by comparing the distribution character of the obtained incremental shear stress (Δγ_xy) field with that of the foci of mid strong earthquakes, we find that there is a certain relationship between the incremental shear stress and the location of these earthquake foci. The fact that the earthquake focus is usually located in the area of severe variation of shear stress increment proves that the simulated tectonic stress field is reasonable to some extent.

Key words: vertical movement, 3-D finite element method, tectonic stress field, shear stress increment