CHINESE JOURNAL OF GEOPHYSICS GPS

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1 CHINESE JOURNAL OF GEOPHYSICS Vol. 46, No. 2 Mar., GPS, GPS,,,,., mmπa. 23Ma, 18mmΠa,,,. GPS (2003) P , A STUDY ON CONVERGENCE RATE OF THE INDIA PLATE TO ERUASIA SUBDUCTION BENEATH QINGHAI2XIZANG PLATEAU INVERSION RESULTS FROM GPS OBSERVATIONAL DATA WANG YONG XU HOUZE Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan , China Abstract The Convergence rate of the India plate to Eurasia subduction beneath Qinghai2Xizang Plateau is inversed on the basis of the GPS data observed by Chinese and abroad Institutes using the model of the India plate to Eurasia subduction and dislocation in two layered self2gravitational elastic half space. Present convergence rare of the India plate is obtained under the geodetic data constrains. The results show that the present convergence rate of the India plate is mmπa with a dipping 8. 1 to the north. This is in good agreement with various geologic predictions of 18mmΠa in past 23 million year implying a stable convergence rate of the India plate in a very long duration. Key words Plate subduction, GPS, Elastic dislocation, Geodetic inversion Qinghai2Xizang Plateau. 1,GPS 10-9,,.,GPS [15 ],GPS, GPS.,.,, ;., ( KZCX2-106) ( ).,,, 1964, 1985,1995,. E2mail : whigg. ac. cn

2 186 (Chinese J. Geophys. ) 46,?,?,.,,.,.,.,, [510 ]. Bilham [5 ]. Jackson [11,12 ] GPS. GPS, GPS, GPS,. 2 GPS GPS, : (1) GPS ( IGS). 48 GPS,. ( ) ( ) (),. (2), GPS, 3, 3., ITRF GPS GAMIT. 1 GPS (3) GPS,,,,14, 1470km, 60km,, Turbo Rogue, GAMIT., IGS,ITRF97 (4) ,, 24, IGS. 1991, 1015mm, ,5 6mm,JPL GIPSY ITRF. (5) ( ) GPS, 6, GAMIT ITRF., 1 GPS [15 ], [610 ]. Table 1 The comparison of GPS observational result consistency in Tibetan Plateau ( ) ( ) ( ) ( ) (mmπa) (mmπa) () [5 ] [2 ] [1 ] [4 ] [1 ] [2 ] [1 ] [2 ] [4 ] [2 ] [4 ]

3 2 : GPS GPS [610 ], GPS [15 ] Fig. 1 The movement vectors of GPS observational points in Qinghai2Xizang Plateau relative to Eurasia plate. Openarrowshowthe velocityofplate andfault determinedfroma varietyof geologic data [610 ] show the movement velocity determined from GPS observation [15 ], solidarrow, GPS,1. 1,,.,1 49 GPS. 3 2 INDEPTH [13 ], 1 GPS,2. 2 [12 ],,,,,., 3 (+ ). [14 ] 2 [13 ] Fig. 2 A model of India to Eurasia subduction [13 ]

4 188 (Chinese J. Geophys. ) 46 3 Fig. 3 Dislocation model of two layered self2gravitational elastic 2 u half space - < - g e z u + g 2 < = - 4G u = 0, ( u e z ) (1) u, (2), u ( r,, z),, e z z, G,, g. (1) (2).,[15,16 ]. j m j,(1) (2) i ( x 0, y 0 ), S i ( m j ) = ( u yi - u y0 ) 2 + ( u xi - u x0 ) 2 = u 2 y i +u 2 x i, f ( m j ) = (u yi - u 0 y ) 2 + (u xi - u 0 x ) 2 i N - j,u 0 y u 0 x GPS, N. m j, m j, (3) (4) a j m j b j, (5) (5), (4) m j. 4 3, 10,L W D U 1 U 2 U 3, 0 < 0. U 3,9. [17 ], (4) (5)., Okada [18 ] (3),,.,. : H 90km, Lame g cm - 1 s - 2, g cm - 3 ;Lame g cm - 1 s - 2, g cm GPS,,,.,, 1 GPS,,. INDEPTH [13 ], 18 7mmΠa [6,7 ],,L = 1500km, W = 500km, D = 50km, U 2 = 30mmΠa. 4. 4,32, 2mmΠa., GPS.,,, (3) S i ( m j ). 2,,,Larson [12 ]

5 2 : GPS Fig. 4 The displacement vector of modeling computation in Qinghai2Xizang Plateau due to the India to Eurasia subduction 2 Table 2 The parameters and results of inversion L W D U 1 U 2 0 < 0 f (km) (km) (km) ( ) ( ) (mmπa) (mmπa) ( ) ( ) (mm) N (1) N (2) N (3) N (1), (2), (3) [12 ]. 5 Fig. 5 The displacement vector computed of Tibet Plateau due to the subduction of India to Eurasia plat from the inversed model parameters GPS GPS. 2, 6 GPS Fig. 6 The residual distribution of the computed displacements with GPS observational results Larson [12 ], f,. 5,GPS GPS ( 1),(6),

6 190 (Chinese J. Geophys. ) 46 10mm,, , N, INDEPTH [13 ] mmΠa. 18mmΠa [6,7 ],.,.,19. 8km, [18,19 ]., 70km. 6080km,.,- 20km,20km, 20km. [12 ],,. [ 1 ],,. GPS., D, 1997, 27(5) : ZHU Wenyao, CHENG Zongyi, XIONG Yongqing, et al. Preliminary results in the monitoring of earth crust motion in Qinqhai2 Xizang Plateau using GPS technology. Science in China, D, 1997, 27(5) : [ 2 ] LIU Jingnan, XU Caijun, SUN Chenghua, et al. Using repeated precise GPS campaigns for research of present2day crustal movement and strain in the Qinghai2Tibetan Plateau. Chinese Science Bulletin, 2001, 48(8) : [ 3 ],,. GPS., 1998, 18 (3) :4350 WANG Qi, YOU Xinzhao, WANG Wenying, et al. GPS measurement and current crustal movement across the Himalaya. Crustal Deformation and Earthquake (in Chinese), 1998, 18 (3) :43 50 [ 4 ],.., 1998, 18 (2) :3642 ZHANG Chijun, XU Daxin. Recent crust movement in middle section of the high Himalaya. Crustal Deformation and Earthquake ( in Chinese), 1998, 18 (2) :3642 [ 5 ] Bilharm R, Larson k, Freymueller J, et al. GPS measurements of pr2 esent day convergence rates in the Nepal Himalaya. Nature, 1997, 336 :6164 [ 6 ] Aarmijo R, Tapponnier P, Mercier J L, et al. Quaternary extension in southern Tibet : Field observations and tectonic implications. J. Geophys. Res., 1986, 91 : [ 7 ] Molar P, Deng Q. Faulting associated with large earthquakes and the average rate of deformation in central and eastern Asia. Res., 1984, 89 : J Geophys. [ 8 ] Molnar P, Lyoncaen H. Fault plane solutions of earthquakes and active tectonics of the Tibetan Plateau and its margins. Geophys. J. Int., 1989, 99 : [ 9 ] Molnar P, Burchfiel B C, Kuangyi L, et al. Geomorphic evidence for active faulting in the Altyn Tagh and northern Tibet and qualitative estimates of its contribution to the convergence of India and Eurasia. Geology, 1987, 15 : [10 ] England P C, Molnar P. The field of curstal velocity in Asia calculated from Quaternary rates of slip on faults. Geophys. J. Int., 1997, 130 : [11 ] Jackson M, Bilharm R. Constraints on Himalayan deformation inferred from vertical velocity fields in Nepal and Tibet. J. Geophys. Res., 1994, 99 : [12 ] Larson K, Burgmann R, Bilham R, et al. Kinematics of the India2 Eurasia collision zone from GPS measurements. J. Geophys. Res., 1999, 104 : [13 ] Zhao W, Nelson K D, INDEPTH Project Team. Deep seismic reflection evidence for continental underthrusting beneath southern Tibet. Nature, 1993, 366 : [14 ] Rundle J B. Static elastic2gravitational deformation of a layered half2 space by point couple sources. J. Geophys. Res., 1980, 85 : [ 15 ] Wang Yong. Theoretical modeling of local gravity changes and deformation caused by dilatancy with magma intrusion. In. Segawa Y et al. eds. Gravity, Geoid and Marine Geodesy, Berlin Heidelberg : Springer2Verlag, 1997, [16 ] Wang Yong, Xu Houze. Surface deformation and gravity changes caused by dilatancy in a layered elastic2viscoelastic half space. Acta Seismologica Sinica, (4) : [17 ],.. :, XING Wenxun, XIE Jinxing. Modern Optimization Algorithm. Beijing : Tsinghua University Press, [ 18 ] Okada Y. Surface deformation due to shear and tensile faults in a half space. Bull. Seism. Soc. America, 1985, 75 (4) : [19 ],,.., 2000, 43(6) : ZENG Rongsheng, DING Zhifeng, WU Qingju, et al. Seismological evidences for the multiple incomplete crustal subductions in Himalaya and southern Tibet. Chinese. J. Geophys. ( in Chinese), 2000, 43(6) :780797