GPS观测约束下的中国大陆活动地块运动学模型

KINEMATICAL MODEL OF CRUSTAL BLOCKS OF CHINA CONTINENT REVEALED BY GPS MEASUREMENTS

利用中国大陆及邻区1683个GPS测站的观测资料,建立由31个活动地块组成的大陆变形运动学模型,这些地块主要以约30条产状各异、滑动速率不等但不高于20mm/a的第四纪活动断层为边界。模拟中将大陆构造变形视为活动地块的刚性旋转和地块边界断层闭锁的弹性变形的综合响应。结果表明,在GPS观测精度内,该模型整体上较好地反映了中国大陆构造变形的主要特征。模型给出的主要断层滑动速率在青藏高原及周边为6～18mm/a,在中国东部地区为1～4mm/a,与地质长期速率比较一致;模拟表明地块内部变形不过10×10-9/a,与50～100km宽的边界带局部变形相比,块体内部变形十分有限。这说明块体的旋转运动而非连续分布变形是大陆构造的主要活动方式,板块构造原则仍可用来刻画大陆变形的运动学特征。

Using the measurements at 1 683 GPS stations in China continent and its adjacent areas,we built a kinematical deformation model of the continent composed of 31 active blocks which are bounded on about 30 Quaternary active faults with different atlitude and slipping rate less than 20 mm/a. In modeling, the tectonic deformation of the continent is regarded as the combination of coherent motion of the relevant block and elastic strain induced by locking of boundary fault. The simulated results show that, in the GPS measurement accuracy range, the model reflects the main features of tectomic deformation of China continent well. The slip rates offerred by the kinematic model of the major faults in Qinghai-Tibet plateau and surrounding area are in ranges of 6 - 18 mm/a and 1 - 4 mm/a in Eastern China, which are consistent with geological observation in long time. The numerical simulation indicates that the internal deformation of crustal blocks compared with the local deformation of the margin zone of 50 - 100 km wide is limited, about 10 × 10 ^-9/a. This suggests that the continental deformation pattern is not continuous-like but block-like, and the plate tectonics principle may still be applicable to characterize the deformation kinematics in Asia.