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

The inversion of modern tectonic stress field in China is made by regions on the basis of focal mechanism data inthe period of 1920-1996. Results of the inversion show that the maximum principal compressive stress σ1 axisstrikes nearly north-south direction in the Tibet Plateau and western Chin4 east-west direction in North China Incentral China, its strikes show a radiate pattern, i.e., north-north east in north part, east-west in central part andnorth-north west in south part. The σ1 axes are often perpendicular to the minimum principal stress σ3 axes, exceptwestern 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 showstrike-slip faulting with intermediate R values, which occupies North China and the eastern part of China as well asinner Tibet Plateau. A few of them show reverse faulting with higher R values within western pod of China and thenorth edge of the Tibet Plateau. Normal faulting occurred on the south edge of the Tibet Plateau with smaller Rval nes.