According to the stress state and force source character, the recent tectonic stress field of China and adjacent regions is classified into four classes: The first order tectonic stress district is mostly controlled by the geometry of plate boundary and the force acting on plate boundary, the stress action of this stress field shows uniformity and stability in large areas and long time. The stress action of second order tectonic stress district shows correlation in a large area. This stress field is controlled by regional block interaction. The stress regime of the third order tectonic stress district shows comparability in finite areas. This stress filed is mostly influenced by interior block interaction inside the areas. The stress character (direction, intensity, regime, etc) of the forth order stress district shows better coherence. This stress filed is mostly controlled by block and fault interaction, and some may be influenced by its crust structure and tectonic environment. Recent tectonic stress field in China and adjacent region is divided into two first order districts, four second order districts, five third order districts and twenty‐six fourth order districts.

The latest hydraulic fracturing and stress relief measurement data of Chinese mainland were collected and supplemented to "Database of Crustal Stress in China and Adjacent Areas" which was established in 2003. They include 3586 in situ stress data collected at 1474 points. The data are distributed in a space of longitudes 75 • E-130 • E, latitudes 18 • N-47 • N, and depths 0∼4000 meters covering all active blocks and of north-south seismic belt which are of great importance in tectonic research. Depth-grouping analysis was made in this paper to solve the problem caused by uneven distribution of measurements in the depth range. The magnitude and direction characteristics of stresses measured in the shallow crust of Chinese mainland and each study area were given. The results were summarized as follows. (1) The magnitudes of maximum horizontal stress, minimum horizontal stress and vertical stress all increase linearly with depth. (2) The lateral pressure coefficient values are scattered in superficial and tend to concentrate with increasing depth to be 0.68. At depth of 465 m, dominance turns from horizontal stress to vertical stress. (3) The magnitude of horizontal differential stress is 3MPa on the surface, which grows with depth at a gradient 5.8 MPa/km. (4) In the middle depth range of measurement data in Chinese mainland (depth 2000 m), the descending order of stress magnitudes in blocks is: 63.6 MPa in Qinghai-Tibet, 57.3 MPa in north section of the north-south seismic belt, 51.4 Mpa in South China, 50.5 MPa in North China, 47.9 MPa in middle section of the north-south seismic belt, 47.5 MPa in Northwest China, 45.4 MPa in south section of the north-south seismic belt, and 44.8 MPa in Northeast China. Generally, stresses are high in west and low in east. This indicates that the India-Eurasia collision determines the general pattern of the tectonic stress field in Chinese mainland. (5) Compared other study regions, the northward crustal compression to the Qinghai-Tibet block is relatively lower magnitudes in the shallow subsurface and higher in deep. (6) Radically oriented maximum horizontal stresses characterize the Tibetan Plateau, the directions of which gradually rotated clockwise from N-S to NNE-SSW, NE-SW, NEE-SWW, NW-SE, consistent with focal mechanism solutions.

: Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In‐situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths (∼20 m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake.

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