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本文总结了近几年来,以改进的水压致裂法,在我国东北、华北、西北和华南的部分沉积岩地区,最深达四千米的二百余测点应力测量结果,并结合震源机制解、地形变、地质和地球物理资料,分析讨论了地应力的空间分布,地震活动区与稳定区的差异,唐山地震前后震源区附近区域应力场的变化以及这些特征的形成与我国周围板块运动的关系。初步研究结果表明,(1)这些地区普遍存在以水平压应力为主的构造应力场,最大主应力方向在我国的东部地区为近东西向,在西北地区为近南北向。(2)深部水平主应力均与深度呈线性关系。(3)垂向主应力一般介于最大与最小水平主应力之间,断层活动多为走滑性质。(4)水平各向应力存在差异性,最大为最小水平主应力的1.2～1.7倍。(5)平均水平主应力与垂向主应力的比值分布,约在二千米深度逐渐从分散转向收敛。地震活动区和稳定区由于水平向驱动力的作用不同,这个比值呈现大于1与小于1的不同特点。(6)地震活动区和稳定区的断层滑动系数亦有所差异,前者在一、二千米深度易于滑动,后者在三、四千米以上深度易于滑动。(7)最大剪应力随深度增加相当缓慢,其梯度低于垂向主应力梯度近一个量级,地震活动区和稳定区的梯度差别达1.5倍。(8)震源区外围附近的区域应力场,大震前呈现的变化为:区域应力场受到
This paper summarizes the recent years, with improved hydraulic fracturing method, in some northeastern China, north China, northwestern and southern China sedimentary rock area, the depth of up to four kilometers of more than 200 measured stress measurements, combined with the focal mechanism solution , Topography, geology and geophysical data. The spatial distribution of geostress, the difference between seismic active area and stable area, the change of stress field in the vicinity of the source area before and after the Tangshan earthquake, and the formation of these features are related to the movement of the surrounding plate in China relationship. Preliminary results show that: (1) There is a widespread tectonic stress field dominated by horizontal compressive stress in these areas. The direction of maximum principal stress is near east-west in the eastern part of China and nearly north-south in the northwest. (2) The deep horizontal principal stress is linear with depth. (3) The vertical principal stress is generally between the maximum and minimum principal stress, and the fault activity is mostly of strike-slip nature. (4) There is difference in horizontal and horizontal stress, the maximum is 1.2 ~ 1.7 times of the minimum horizontal principal stress. (5) The distribution of the ratio of the average principal stress to the vertical principal stress gradually shifts from dispersion to convergence at a depth of about 2 km. Seismic areas and stable areas due to the role of horizontal driving force is different, the ratio showed more than 1 and less than 1 different characteristics. (6) There are also differences in the fault slip coefficient between the seismic activity zone and the stable zone. The former slides easily at the depth of 1 and 2 km and the latter slides easily at depths of more than 3 and 4 km. (7) The maximum shear stress increases slowly with depth, its gradient is lower than the vertical principal stress gradient by nearly a magnitude, and the gradient difference between the seismic activity zone and the stable zone reaches 1.5 times. (8) The regional stress field near the periphery of the focal zone shows the changes before the earthquake: the regional stress field is affected