Analysis of the Motion of the Kunming GPS Station Relative to the Eurasian Plate

The deformation rates of the Kunming GPS station are as follows: the vertical deformation rate is (-4.3±0.5mm)/a(down),and the horizontal components are 31.5 and-20.4mm/a at east and south directions respectively revealed by the international cooperation survey.In order to accurately confirm the relative deformation and steady character of the Kunming station,in this paper,a new present-day global plate motion ITRF2000VEL is determined on the basis of space geodetic data,incorporating with the ITRF2000 velocity field that is free of any additional tectonic plate model assumption,with respect to the ITRF96 and ITRF97.The quantity and quality of ITRF2000 station velocities have been largely improved and also the distributios are more and more spreaed.For example,the total number of sites increases from 500 in ITRF97 to 650;except the collocated sites,the number of sites also increases form 320 to 370.Therefore,ITRF2000 can provide more reasonable and more precise plate motion model than ITRF97 and ITRF96.The global plate motion model of ITRF2000VEL is determined from an about 20-year time span of the space geodetic data. Hence the model can better describe contemporary features of global plate motion than the geological model NNR-NUVEL1A that was determined based on the geological and geophysical data in several million years.In addition,the ITRF2000VEL model is almost consistent with the geological model NNR-NUVEL1A,but there are differences of about 10 percent rotation magnitude and 15 degree between the Euler vectors of the two models.These differences are very significant for contemporary crustal deformation measurement in mm/yr accuracy.The ITRF2000VEL model is more suitable as the background of deformation investigation for current short time scale than the NNR-NUVEL1A. By analyzing the deformation of the Kunming GPS Station related to the Eurasian Plate based on the Euler Vector of ITRF2000VEL the vertical deformation rate of the Kunming GPS station is obtained as -0.01 mm/a(down),the horizontal component is 8.1±0.20 mm/a with its local azimuth of 137°±1.5°;Moreover,based on the Euler vectors of the Eurasian plate of the NNR-NUVEL1A,ITRF96VEL,ITRF97VEL,respectively,the similar results are gained,which shows that the motion of the Kunming station related to the Eurasia is stable and reliable. Because the Kunming station lies in among the India plate,Philippines sea plate,Tibet plate and North China plate,the inter-plate deformation and interaction between blocks are very complicated.Study of the deformation of the Kunming station in the South China is very important to know the motion character of the South China,but more accurate deformation of the Kunming station at a few millimeters per year level depends on the denser and more accurate space geodetic measurements with longer observation time span in Kunming areas in the future.