The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evolution of Euro-Asian continent, which resulted in the formation of the present range-and-basin pattern in topography of the Tianshan Mountains and its adjacent areas. Thermochronology results by the method of fission-track dating of apatite suggest three obvious uplifting stages of the Bogad Mountain Chain re-orogeny during the Cenozoic, i.e. 5.6-19 Ma, 20-30 Ma, and 42-47 Ma. The strongest uplifting stage of the mountain is the second one at 20 -30 Ma, when the mountain uplifted as a whole, and the beginning of re-orogeny was no less than 65 Ma. Furthermore, our studies also show that the uplifting types of the mountain are variable in the different time periods, including uplifting of mountain as a whole and differential uplifting. The apparently diversified uplifting processes of the mountain chain are characterized by the migration (or transformation) of the uplifting direction of the mountain from west to east and from north to south, and the main process of mountain extending is from north to south.

Based on joint processing to the observation data of various GPS networks during 1991~1999 and basic network of China Crustal Movement Observation Network during 1998~2000, horizontal velocities in the China mainland have been calculated. Using this result, assuming medium to be continuous, and by establishing model for horizontal velocity field with the aid of the least square collocation, we have acquired the horizontal strain fields (or called apparent strain fields) of the China mainland. Then, we have analysed the characteristics of spatial distribution of horizontal motion and strain field, as well as their relationship to major earthquakes, and give a brief analysis for tectonic deformation background of the MS8.1 earthquake on the west of Kunlun‐mountain pass on Nov.14, 2001. The results show that strong tectonic deformation and high strain rates occur in mid‐western China, which are most remarkable in the Qinghai‐Xizang block and its margins and western Xinjiang. In most areas, except Sichuan‐Yunnan and western Xinjiang, nearly EW trending faults have sinistral shear deformation, and nearly NS trending faults show dextral shear deformation. However, eastern China indicates weaker tectonic deformation. Generally strong earthquakes occur in the region and its margins of high‐value shear strain rate, especially in the region of high‐value shear strain rate in accordance with tectonic deformation background. The MS8.1 earthquake at the west of Kunlun‐mountain pass happened in the most obvious high‐value region of east‐westward sinistral shear strain rate, and this region has tectonic deformation background that nearly EW trending faults produce dislocation of huge strike‐slip ruptures as inferred from the strain state.

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