Modern tectonic stress field in the Chinese mainland inverted from focal mechanism solutions

Abstract

The inversion of modern tectonic stress field in China is made by regions on the basis of focal mechanism data in the period of 1920–1996. Results of the inversion show that the maximum principal compressive stress σ₁ axis strikes nearly north-south direction in the Tibet Plateau and western China, east-west direction in North China. In central China, its strikes show a radiate pattern, i.e., north-north east in north part, east-west in central part and north-north west in south part. The σ₁ axes are often perpendicular to the minimum principal stress σ₃ axes, except western China where the σ₁ axes are oblique to the σ₃ axes with an acute angle. R is defined by (σ₂-σ₁)/(σ₃-σ₁), has the higher values (0.60–0.90) in north part of central China and quickly changes into the lower values (0.10–0.30) in the Tibet Plateau. Both of the observed and inverted fault planes have strikes varying with locations. Combining stress directions and R value, the stress configuration is divided into 7 groups. Most of the groups show strike-slip faulting with intermediate R values, which occupies North China and the eastern part of China as well as inner Tibet Plateau. A few of them show reverse faulting with higher R values within western part of China and the north edge of the Tibet Plateau. Normal faulting occurred on the south edge of the Tibet Plateau with smaller R values.