In Situ Measurements and Comprehensive Research on the Present Crustal Stress of Northern South China Sea

• Published in: Chinese journal of geophysics 2014-07, Vol.57 (4), p.462-473
• Main Authors: Qun-Ce, CHEN, Tao-Yuan, FAN, Xu-Shen, LI, Sheng-Lin, HE, Chong-Yuan, ZHANG, Wen, MENG
• Format: Article
• Language: English
• Subjects: Basins; China; Crustal stress; FE Modeling; FMI; Geophysics; Hydraulic fracturing; Mathematical models; Northern South China Sea; Oceans; Philippines; Rock; Stresses
• ISSN: 0898-9591; 2326-0440
• DOI: 10.1002/cjg2.20117

It is necessary for developing of ocean resources, safety evaluation of geological environment and engineering to understand the status and distribution of present crustal stress in the northern South China Sea. The nature conditions restrict the research on the crustal stress of the whole South China Sea, whose characters and controlling factors are not clear. In situ stress measurement is a useful way to get the stress magnitude and direction. The stress direction can be got through the logging FMI data in ocean oil field. The numerical modeling can extrapolate the stress status and distribution in the interested area under the constraint of the in situ measured stress, FMI deduced stress and the plate tectonic environment. The west bound of northern South China Sea is Red River Fault‐Eastern Vietnam strike slip large Fault which is controlled by the collision of India plate and Euro‐Asia plate and the uplift of Tibet. The east bound of northern South China Sea is Manila trench, which have three different tectonic stress sections, plate collision near Taiwan and near Luzon, and extension between Taiwan and Luzon induced by South China Sea subduction under the Philippines plate. The authors measured in situ the magnitude and direction of stress in Ledong county, Hainan province through hydraulic fracturing, where the exposed rock body is intact and the landform is gentle. The measured rock in well is intact and the curve of measured pressure is fit to the standard, which shows that the measured stress is reliable. The optimal direction of measured maximum stress is NW‐NWW. According to the Byerlee criteria, the measured stress cannot induce the active fault to be reactivated recently. The logging FMI interpretation of marginal oil basin in the northern South China Sea shows that the optimal direction of maximum principal stress is NW‐NNW in Yinggehai basin, and NNW in Qiongdongnan basin. Constrained by the in situ measured stress and the focal mechanism the numerical modeling shows that the crustal stress in northern South China Sea is characterized by the different stress status in different zone due to India plate, Euro‐Asia plate and Philippine plate playing different role. In the area near Taiwan the crustal stress is dominated by the collision of Philippe plate and Euro‐Asia plate, and the direction of maximum principal stress is E‐W. Along marginal northern South China Sea the crustal stress is influenced by extension induced by the Euro‐Asia plate