In-situ stress state in the China’s Sea and adjacent areas

Based on 141 data of in-situ stress orientations data of breakouts, stress reliefs and hydraulic fracture tests, and some data of stress magnitudes from oil-well hydrofracturing operations, this paper discusses in-situ stress regime and the tectonic stress provinces in the China’s Sea and adjacent areas. Furthermore, the origin of tectonic stress field is expounded. The research results show that the tectonic stress in China’s Sea region can be divided into some stress provinces which are the extension of the Northern China and Southern China stress provinces toward the eastern sea area. The tectonic stress field in the Bohai and Huanghai and their neighbouring regions is controlled by a ENE-WSW compression, where the faulting types are mainly strike-slip. However, the stress in the East and South China’s sea region and the Taiwan Straits is dominated by the WNW-NW-NNW compressions, that is to say that the orientations of the maximum horizontal stress spread radially from the central mainland toward southeastern sea areas. The principal stress directions become more and more steady and uniform as depth increases. In the North China and nearby areas, the types of faulting are primarily strike-slip. In Southern China and adjacent sea areas, there is a transition layer at 1,700M depth, the faultings principally show reverse faults above that depth and strike-slip below it. Furthermore the origin of the tectonic stress field in this region may primarily come from the composite action of the Pacific, the Philippine sea and the India-Australian plates.