Velocity And Strain Rate Field Of The Crust In The China Continent From Quaternary Active Fault Observations

The China continent lies among the Pacific, India and Philippine plate and its movement and deformation reflect important regularity of crust movement. It attracts much attention of geo-scientists in the world. To get an accurate velocity field of crust motion in the China continent is of great importance in understanding collision effects between continents and global crustal movement.Since 1950s, geo-scientists of different counties have done lots of fruitful work on the China continent and got lots of quantitative data about active faults. All the data obtained by previous researchers make it possible to study the dynamics of China continent systematically with quantitative methods.Active faults are important expression of intra-continental crustal deformation. By analyzing the distribution features, geometric structures, active characters and magnitude of active faults in China and its adjacent regions, the horizontal strain rates of crustal deformation can be obtained. Based on these data and using Haines' method, the distribution of horizontal strain rates and crustal deformation velocity field of the China continent can be calculated.In recent decades, lots of quantitative data about actives faults in China are acquired by geological investigation. The strain rate and velocity field of crustal deformation can be calculated by Haines' method with these data. The goal of this work is to get the features of crustal movements of the China continent.In this study, the following methods are adapted.First, data of active faults are collected and sorted by their magnitude and significance.Second, an analyse is made to the obtained data of the active faults. The process is using the data of the latitude, longitude, dip, minimum slip rate, average slip rate, and maximum slip rate of the active fault to represent its active character and velocity. The minimum slip rate, average slip rate and maximum slip rate can cover the recent results of geological research and can reflect the real activity of the selected faults.Third, the active faults in the China continent are delineated according to the previousstudies and the curvilinear grid is constructed for the calculation model according to distribution of active faults in China continent.Fourth, the Haines's method is used to calculate the strain rates and velocity fields of crustal continental deformation on the China continent with reasonable assumption of boundary conditions.Fifth, based on the above results, the distribution of strike-slip strain rate, dilatational rate, rotation rate and moment rate of China continent are calculated and the regularities of crustal deformation of the China continent are summarized. The main conclusions of this thesis are described below.The crustal deformation velocity field calculated from the movements of Quaternary active faults is consistent with the results of GPS (global positioning system) observation. The movement of the China continent of present is stable and does not change obviously compareing with the movement during Quaternary.The collision between India plate and Eurasia plate and the northward movement of the India plate cause uplift and northeastward motion of the Tibetan Plateau. Relatively, the influence from the Pacific plate and the Philippines plate to the China continent is much smaller than that from the India plate. The strain rate and the velocity field of the China continent become smaller from west to east.The deformation of the China crust is characterized by motion of active crustal blocks. Main active faults in China absorbed most deformation of the China continent. It is the boundaries of active crustal blocks that have the stronger deformation than the inside of them. The active faults listed in this thesis absorb about 90 percent crustal deformation. The other deformation is assimilated by other small or unknown faults. In the model of this study the northward motion rate of the India plate calculated from main active faults data is only about 35mm/a. When the incomplete fac...