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摘要
The latest hydraulic fracturing and stress relief measurement data of Chinese mainland was collected and supplemented to the "Database of Crustal Stress in China and Adjacent Area" which was established in 2003. The entries of in situ stress data measured at 1474 points are 3586. The longitude, latitude, and depth range is 75 degrees E-130 degrees E, 18 degrees N similar to 47 degrees N and 0 similar to 4000 meters respectively. Every active block and each section of north-south seismic belt have data more or less. Depth-grouping analysis was used in this paper to solve the problem caused by uneven distribution of measurement data along the depth. The magnitude and direction characteristics of stresses measured in the shallow crust of Chinese mainland and each study area were given. The result is summarized as follows. (1) The magnitudes of maximum horizontal stress, minimum horizontal stress, and vertical stress all increase linearly with depth; (2) The characteristics of the lateral pressure coefficient with depth can be described as follow. The distribution of K-av is scattered in superficial crust, becomes more concentrated in the deeper crust and trends to 0. 68. At a depth of 465 m K-av equals to 1 which indicates the transition from horizontal to vertical stress domination. (3) The magnitude of horizontal differential stress equals to 3 MPa at surface. The growth gradient is 5. 8 MPa/km. (4) In the middle depth range of measurement data in Chinese mainland(i.e. depth equals to 2000 meters), the descending order of stress magnitudes in various blocks is: 63.6 MPa in Qinghai-Tibet, 57.3 MPa in north section of north-south seismic belt, 51.4 MPa in south China, 50.5 MPa in north China, 47.9 MPa in middle section of north-south seismic belt, 47.5 MPa in northwestern China, 45.4 MPa in south section of north-south seismic belt, and 44.8 MPa in northeast China. Generally, the basic characteristic of magnitude is high in west and weak in east. This indicates that the strong collision of Indian plate and Eurasian plate determines the general strength characteristics of tectonic stress field in Chinese mainland. (5) Compared to most other study regions, the crustal stress magnitude feature of the Qinghai-Tibet block under northward compression is lower in the shallow and higher in the deep. (6) The general direction characteristics of maximum horizontal stress basically spread radially from the center of Tibetan Plateau. The directions of maximum horizontal stress gradually rotate clockwise from N-S to NNE-SSW, NE-SW, NEE-SWW, NW-SE and are consistent with the result of focal mechanism solution.
- 出版日期2012-12
- 单位中国地震局; 中国地质科学院地质力学研究所
