Current structural deformation characteristics and GPS velocity field of the Qinghai-Tibet Plateau Zhang Peizhen 12, Wang Qi 3, Ma Zongjin 12 (1. Institute of Geology, China Earthquake Administration, Beijing 100029; 2. GPS Open Research Center, China Earthquake Administration, Beijing 100029; 3. China Earthquake Institute of Seismology, Wuhan 430071, Hubei, China), and explored the state and mechanism of the deformation and the internal dynamics of the continent reflected by the current structural deformation of the Qinghai-Tibet Plateau. The velocity vectors observed by GPS reveal the overall north and east movement of the Tibetan Plateau. The crustal shortening parallel to the collision direction of the Indian and Eurasian plates is about 38 mm / a, and the slip rates of the main fault zones around the Tibetan Plateau are at 10mm / a or less. About 90% of the relative movement of the Indian and Eurasian plates is absorbed and regulated by the crustal shortening of the Tibetan Plateau. The GPS velocity vector gradually deflects from south to north, and the eastward component also increases, forming two crustal material directions centered on the northern Qiangtang block (or Mani-Yushu-Xianshuihe fault) and the central Qilian Mountains East flow belt. The eastward extrusion of the Qinghai-Tibet Plateau is actually a clockwise rotation of the crustal material around the east tectonic junction under the push of the Indian plate and blocked by the surrounding rigid blocks.
4: A Article number: 1005-2321 (2002) 02 The collision between the Indian and Eurasian plates in the early Cenozoic and the subsequent entry of the Indian plate is a brilliant page in the history of the evolution and evolution of the Cenozoic Earth. Convergence between the continuous and powerful plates is decomposed and absorbed by the crustal shortening from the Tibetan Plateau to the Tianshan Mountains with a width of several thousand kilometers and the eastward extrusion of the crustal blocks in the eastern Tibetan Plateau. Therefore, the structural deformation and evolution of the Late Cenozoic on the Qinghai-Tibet Plateau has always been the core and frontier hotspot of international continental dynamics theory research.
Many existing theories and hypotheses can be basically divided into two categories.
The first type is the theory represented by continental escape, and it is believed that the continental deformation is mainly based on the strike-slip motion along the huge faults and the lateral sliding of the block.
The 7 measuring points of the Qiangtang block show movement towards the dominant direction of about NE60 *, with an average rate of (28 * 5) mm / a, which is different from the Lhasa block south of it. There is only one observation station (WUDA) on the Kunlun block to the north, with a movement direction of about 61.45 ° and a velocity of about 21mm / a. The Qaidam active block north of the Kunlun block although the movement direction is not the same as the Kunlun block There is a big difference, but the average speed of movement suddenly drops to 12 ~ 14mm / a. And then to the north to the Qilian Mountain active block, the dominant movement direction becomes 70 * ~ 90 °, and the speed decreases to 7 ~ 14mm / a. Therefore, the movement of the active plots within the Qinghai-Tibet Plateau is divided into blocks, with different movement directions or speeds.
2 The crustal shortening of the Tibetan Plateau The strong crustal shortening is the most significant feature of the Late Cenozoic tectonic deformation of the Tibetan Plateau. Not only its average altitude reaches 5000m, but also a huge continental crust with a thickness of 60 ~ 70km, which is higher than the 35km continental The crustal shortening caused by the collision of the Eurasian continent is the fundamental cause of the crustal thickness of the Qinghai-Tibet Plateau. Is the current tectonic deformation of the Tibetan Plateau still characterized by crustal shortening? The crustal shortening rate accounts for the relative movement rate of the Indian and Eurasian plates. How many, these questions are of great significance for understanding the structural deformation of the Qinghai-Tibet Plateau and the mainland, and testing various theoretical models.
The global plate tectonic movement model shows that the relative movement direction between the Indian and Eurasian plates is around NE20 *. Parallel to NE20. Make a GPS velocity profile along the Qinghai-Tibet Highway from the Ganges Plain to the Alxa Massif in India. The GPS velocity vector along the line is decomposed into velocity components parallel to and perpendicular to NE20 *. The velocity component parallel to the relative motion direction of the plate represents the crustal shortening rate across the Tibetan Plateau, and the component perpendicular to the motion direction of the plate represents the lateral extrusion speed of the Tibetan Plateau. It is clearly shown that the difference in relative motion between the Ganges Plain and Alxa block in India is about 38 mm / a, accounting for about 90% of the relative motion speed between the Indian and Eurasian plates. That is to say, India and Europe 90% of the relative movement between sub-plates is absorbed and regulated by the current crustal shortening rate on the Tibetan Plateau. As shown, a Himalayan thrust belt on the southern boundary of the Tibetan Plateau has absorbed a shortening rate of 10-13 mm / a, and the remaining crustal shortening rate of 26-28 mm / a is completed by deformation and shortening inside the Tibetan Plateau.
——Rul- / Indium, Diji, Yaluzangbu, ssk, Karakorum-Jiali fault zone, the original block at the site of the Yalaya Plateau, Shanshan Gaoma Maheng, the original Lala River The clockwise rotation of the eastern Qinghai-Tibet Plateau around the eastern Tibetan Plateau of the southern Qilian fault zone by the Aqiqing high and low level of the Lianzang Xixidu provides another possible explanation (). It can be seen that the movement direction of the GPS observation station east of the Himalayan East tectonic junction is NE45 * ~ 55 °, and it gradually changes from NE65 * ~ 80 * (SOXI, GNGBYUSH, QUER) to the west of Sichuan to the east of the East tectonic junction SE105 * ~ 115 * (XIAL, QIAN, XINL, LTAN), along the eastern boundary of the Qinghai-Tibet Plateau to the south to the south of the Sichuan-Yunnan rhombic block, and then further to SE120 * ~ 135 * (MIAN, CHUX, KUNM, DAYA) and then south The western Yunnan area southeast of the eastern tectonic junction turned to SE155 * ~ 165. (YANGYUHL, BAOS, TENG) The velocity difference between the eastern boundary of the Qinghai-Tibet Plateau and the South China block was not converted into thrust and crustal shortening, but was clockwise Rotate to adjust and absorb. Geological structure and seismic activity studies also revealed this clockwise rotation movement. Unlike the eastward extrusion model proposed by the predecessors, the eastward extrusion or flow of the Qinghai-Tibet Plateau did not exceed its eastern boundary, but it was converted into a clockwise rotation of 20 ~ 30mm / a around the Himalayan east tectonic junction on the eastern boundary. The results are very different. The results in this paper support a low sliding rate of 5 mm / a.
The Qilian Mountains on the northeastern boundary can be regarded as a broad left-handed shear zone. We have given a long-term average slip rate of (7.8 * 1.2) mm / a across the entire Qilian Mountains.
As mentioned earlier, the Longmenshan fault on the eastern boundary has almost no eastward thrust. The velocity difference between the eastern edge of the Qinghai-Tibet Plateau and the South China block observed by GPS and the left-handed strike-slip of the Xiaojiang fault may be due to the Tibetan Plateau surrounding the east The structural knot rotates clockwise resulting in time 29 ,.
In addition to these boundary faults, the movement speed of the South China Block in the eastern part of the Qinghai-Tibet Plateau relative to stable Siberia is also meaningful for studying the dynamics of mainland China. According to the "continent escape" hypothesis, the motion rate of South China should be gradually reduced from 20 to 30 mm / a. The relative motion difference between the Ganges Plain and Alxa block in India is about 38 mm / a, which accounts for about 90% of the relative velocity between the Indian and Eurasian plates. Since the velocity component of the relative motion of the parallel plates represents the crustal shortening rate, 90% of the relative movement between the Indian and Eurasian plates is absorbed by the current crustal shortening rate on the Tibetan Plateau And regulation. The slip rates of the main fault zones around the Qinghai-Tibet Plateau are all below 10 mm / a, which may not be the main structure that absorbs the convergence of the Indian and Eurasian plates.
The direction of movement is gradually deflected from about NE20 * on the Ganges Plain of India to the north, and the eastward component is also added. The Mani-Yushu area in the middle of the Tibetan Plateau is the largest, the direction is about NE75 *, and the east-west speed is about 25mm / a; northward across the Kunlun and Qaidam blocks, the movement direction is changed to about NE60 *, and the east-west movement speed is reduced to 11 ~ 16mm / a. The north of the Qiangtang block (or Mani-I) is generally formed The Yushu-Xianshuihe fault) centered the eastward flow of crustal material, reflecting the eastward migration of the Qinghai-Tibet Plateau. To the north, another flow belt to the east of the crustal material is formed around the main peak of Qilian Mountain, but the scale of this flow belt is much smaller than that of the central Tibetan Plateau. Therefore, the eastward extrusion of the Qinghai-Tibet Plateau is actually a clockwise rotation of the crustal material around the east tectonic junction under the push of the Indian plate and blocked by the surrounding rigid blocks.
Continental tectonic deformation is different at different depths. The upper crust is dominated by brittle deformation, which is manifested as integral (or rigid) block movements and block interactions. The lower crust and upper mantle are viscoplastic. The flow becomes characteristic. The crust of the Qinghai-Tibet Plateau is extremely thick, the average velocity in the crust is lower than normal, the Q value in the crust is low, the geothermal activity is strong, and the surface heat flux value is high. These characteristics indicate that the crustal plasticity of the Tibetan Plateau is high. The northern part of the plateau is the Tarim Basin and the Alashan block, the northeast is the Ordos block, and the eastern part is the Sichuan Basin (South China block). These blocks are relatively stable geological bodies. In the process of the Indian plate pushing north-north-east, these blocks blocked the expansion of the weak or highly plastic Tibetan Plateau to the north and east, resulting in the thickness and shortening of the Tibetan Plateau's own crust, and Rotate clockwise around the east tectonic junction.
The author pays no tribute to all Chinese and foreign observers involved in GPS field operations and tracking station maintenance. Thanks to JTFreymueller, RogerBi Buham, KMLarson for assistance in data exchange and data processing.
Xie Peter Molnar's discussion on the dynamics of continental internal structural deformation and the strong support of the University of California Shen Zhenkang and Fang Peng in data analysis.
Xie Institute of Geology, Dr. Zhiqiang Li's help in computer and drawing.
The ranking of 1993 impact factors and total citations of the latest earth science journals (according to the China Institute of Science and Technology Information, November 2001) (excluding geology and geography) ranking journal names impact factors ranking journal titles total citation frequency geosciences Journal of Frontier Geophysics, Quaternary Research, Journal of Geochemical Geosciences, Surveying and Mapping of Quaternary Research, Geophysics, Journal of Seismology, Journal of Natural Disasters, Frontier Earthquake Engineering and Engineering Vibration Chinese Journal of Desert Crustal Deformation and Earthquake, Journal of Earthquake Research and Surveying, Earth Journal of Wuhan University of Surveying and Mapping, Journal of Seismology, Earthquake Science and Engineering of China Earthquake Engineering Journal of Seismology and Geosciences of China Journal of Microbial Paleontology, Journal of Earthquake Engineering Disaster Science, Space Science Journal of Northwest Seismology, Journal of Land Resources and Remote Sensing, Space Science Journal of Paleontology Bulletin of Geochemical Exploration of Arid Regions, Minerals, Rocks, and Geochemistry. World Earthquake Engineering, Northwest Seismological Journal, Inland Earthquake, South China Earthquake, Geophysics, Surveying and Mapping, Seismic Geomagnetic Observation and Research, North China Earthquake Science, South China Earthquake Geophysics Resource Remote Sensing Geophysical and Geochemical Surveying and Mapping Project
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