Research On Vertical Deformation Of Tienshan Region Based On GPS And Leveling Observation

Although Tien Shan is one of the youngest mountains in Asia, the researches aboutthe tectonic deformation of Tien Shan had been last for about a hundred years.Because of the researchers’s efforts, a lot of fruitful results had been gained. Since theCenozoic, the Indian plate and Eurasian plate collide at the Himalaya, and thanks tothe convergence between Tarim block and Jungar block, it is showed that Tien Shan’stectonic deformation is characterized by N-S shortening across the mountain andthrusting on both edges of the mountain. The convergence not only led to the basins’subsidence and the mountain’s uplift, but also caused many destructive earthquakes,and this is what the famous Tien Shan N-S seismic belt made of.Tectonic movement of Tien Shan area is representative, and it’s in theearthquake-prone belt. Because for many years there aren’t any big earthquakesoccurred in this area, so it is possible that there will be one some day. So studying theregional tectonic activity is more practical.In order to reduce the harms brought by the earthquake as much as possible, thispaper focuses on the research about the relationship between plate tectonics and theearthquakes. The main contents can be divided into three parts:The first part explained the GPS’s principle and origin, positioning method,reference frame, sources of error and GAMIT/GLOBK. And it evaluated the data’sprecision. Most of site velocities used in the paper are better than2mm/yr in precision,being reasonably to meet the needs of further tectonics studies.The second part is based on the first part. Using the collected data of Tien shanfrom1999to2012, we can calculate them with GAMIT/BLOBK to draw the velocityfield of Tien shan, study the interaction of the blocks and the earth’s crust shorteningform.The GPS data reveal that a shortening rate as larger as20mm/yr is confirmed forwestern Tien Shan,15mm/yr for the middle section of Tien shan, and for eastern TienShan, the shortening rate is as small as only less than5mm/yr. And the rates ofconvergence deformation across the Tien Shan demonstrates a linear eastwardtapering. The strain across the Tien Shan also exhibits a heterogeneous distributionalong the direction of compression. And vertical velocity field presented that at themountain-basin junction, the basin descends, and the mountain rises, which revealsthat Tarim block are wedging in Tien Shan continuously.The third part collected and analyzed the leveling data which across the faults from2001to2011, the vertical change represented the style of each faults before and afterthe earthquakes to some extent, and it contains certain earthquake precursorinformation. The result reveals that even in the same fault zone, the vertical velocityand deformation accumulation of the different measurement sections may be verydifferent; and the “N” glyph contained in the data before and after earthquakes are ofa certain reference value in the discoveries and researches of earthquakes.In this paper, the results shows the characteristics of Tien shan’s Tectonic deformation, i hope to deepen the earth dynamics research in Tien shan in this field,reduce the serious damage caused by earthquakes, and make efforts for Xinjiang’sdevelopment.