PROGRESS IN APPLICATION OF GNSS TO DIVISION OF ACTIVE TECTONIC BLOCKS IN CONTINENTAL CHINA

Chinese scientists proposed that large earthquakes that occurred in mainland China are controlled by the movement and deformation of active tectonic blocks. This scientific hypothesis explains zoned phenomenon of seismicity in space. The active tectonic blocks are intense active terranes formed in late Cenozoic and late Quaternary, and the tectonic activity of block boundaries is the intensest. Global Navigation Satellite System(GNSS)has advantages of high spatio-temporal resolution, broad coverage, and high accuracy, and is utilized to monitor contemporary crustal deformation. High accuracy and resolution of GNSS velocity field within mainland China and vicinities provided by previous studies clearly demonstrate that different active tectonic blocks behave as different patterns of movement and deformation, and block interaction boundaries have intense tectonic deformation. The paper firstly introduces the GPS networks operated by the Crustal Movement Observation Network of China(CMONOC)since 1999, and GNSS data processing methods, including GAMIT, BERNESE and GIPSY/OASIS, and discusses the advantages of using South China block as a regional reference frame for GNSS velocity field, then proposes three strategies of block division, F-test, quasi-accurate detection(QUAD), and clustering analysis. Furthermore, we introduce rigid and non-rigid block motions. Rigid block motion can be denoted by translation and rotation, while non-rigid block motion can be described by rigid motion and internal strain deformation. Internal strain deformation can be divided into uniform and linear strains. We also review the usage of F-test to distinguish whether the block acts as rigid deformation or not. In addition, combining with recent GNSS velocity results, we elaborate the characteristics of present movement of rigid block, such as the South China, Tarim, Ordos, Alashan, and Northeast China, and that of non-rigid block, such as the Tibetan plateau, Tian Shan, and North China plain. Especially, the Tibetan plateau and Tian Shan seem to deform continuously with significant internal deformation. In order to enrich and perfect the active tectonic block hypothesis, we should carefully design dense GNSS networks in inner blocks and block boundaries, optimize utilizing other space geodesy technologies such as InSAR, and strengthen combining study of geodesy, seismogeology and geophysics. Through systematic summary, this paper is very useful to employing GNSS to investigate characteristics of block movement and dynamics of large earthquakes happening in block interaction boundaries.