Using the tendentious accumulation rate of crustal deformation,DC,the spatial distributionfeatures of deformation across fault in the West of China was studied;the regional patterns ofdeformation accumulation induced by fault activity was established and its seismogenicmeaning was discussed.The types of fault deformation evolution in the time domain and thefeatures of change of large extent anomaly in fault deformation which occurred in 1995～1996was analyzed comprehensively.It was indicated definitely that 1995～1996 is the turningpoint of fault network activity in the West of China since the 1990s;it is closely related to thechange of main seismic active regions in the West of China,i.e,the alternation of strong/weak stages and the change of action range of tectonic stress field in the Qinghai-Tibet blockand its environs;and hence it is of medium-and short-term precursor meaning for the changeof the overall pattern of earthquake activity in the West of China in the year 1996.On such abasis,a
We obtain the preliminary result of crustal deformation velocity field for the Chinese con-tinent by analyzing GPS data from the Crustal Motion Observation Network of China (CMONOC), particularly the data from the regional networks of CMONOC observed in 1999 and 2001. We de-lineate 9 tectonically active blocks and 2 broadly distributed deformation zones out of a denseGPS velocity field, and derive block motion Euler poles for the blocks and their relative motionrates. Our result reveals that there are 3 categories of deformation patterns in the Chinese conti-nent. The first category, associated with the interior of the Tibetan Plateau and the Tianshan oro-genic belt, shows broadly distributed deformation within the regions. The third category, associatedwith the Tarim Basin and the region east of the north-south seismic belt of China, shows block-likemotion, with deformation accommodated along the block boundaries only. The second category, mainly associated with the borderland of the Tibetan Plateau, such as the Qaidam, Qilian, Xining(in eastern Qinghai), and the Diamond-shaped (in western Sichuan and Yunnan) blocks, has thedeformation pattern between the first and the third, i.e. these regions appear to deform block-like,but with smaller sizes and less strength for the blocks. Based on the analysis of the lithosphericstructures and the deformation patterns of the regions above, we come to the inference that thedeformation modes of the Chinese continental crust are mainly controlled by the crustal structure.The crust of the eastern China and the Tarim Basin is mechanically strong, and its deformationtakes the form of relative motion between rigid blocks. On the other hand, the northward indentation of the Indian plate into the Asia continent has created the uplift of the Tibetan Plateau and the Tianshan Mountains, thickened their crust, and raised the temperature in the crust. The lower crust thus has become ductile, evidenced in low seismic velocity and high electric conductivity observed. The brittle part of t
WANG Min (王 敏) SHEN Zhengkang (沈正康) NIU Zhijun (牛之俊) ZHANG Zusheng (张祖胜) SUN Hanrong (孙汉荣) GAN Weijun (甘卫军) WANG Qi (王 琪) REN Qun (任 群)
