Quantitative analysis of the shallow crustal tectonic stress field in China mainland based on in situ stress data

Abstract

The latest hydraulic fracturing and stress relief measurement data in the Chinese mainland were collected. The total of 3856 data entries are measured at 1474 locations. The measured area covers 75–130°E and 18–47°N, and the depth range varies from surface to 4000meters depth, which generally includes each active tectonic block of China and each segment of North–South seismic belt. We investigated the tectonic stress field by removing the effect of gravity. For this, we assume lateral constraints and Heim’s rule. The gravity contribution is removed by using the assumption of lateral constraint and Heim’s rule. Our results show: (1) the maximum and the minimum horizontal principal stress σH, σh and the vertical stress σV in the shallow crust of China all increase linearly with depth: σH=0.0229D+4.738, σh=0.0171D+1.829, σV=0.0272D. Maximum and minimum horizontal tectonic stress varies as a function of depth D linearly 4.738<σT<0.0139D+4.738 and 1.829<σt<0.0162D+1.829. The horizontal tectonic differential stress is σT−σt=0.0058D+2.912. (2) The intermediate value of σT1 (regression value of tectonic stress inferred from the assumption of lateral constraint at 2000 m depth) changes in different areas, the maximum value of which is 45.6MPa, while the minimum value of which is 26.8MPa. Horizontal tectonic differential stress σT−σt increases linearly with depth and the maximum and minimum of σT−σt is 25.3MPa and 13.0MPa, respectively. In general, the stress magnitude is much higher in western than in eastern China. This indicates that the strong Indo-Eurasian collision dominates the present tectonic stress field in Chinese mainland. (3) Compared with other study regions, the northward crustal compression to the Qinghai-Tibet block is relatively lower in magnitude in the shallow subsurface and higher at deeper depth. (4) The orientations of σT in China mainland generally form a radial scattering pattern centered in Tibetan Plateau. From western to eastern China, they rotate gradually clockwise from NS to NNE, NE, NEE, and SE, which is consistent with the result of focal mechanism solutions.