| Since the application of GPS in the field of geodesy,relevant research in various fields has provided very valuable data support.These data play an important role in the fields of GPS time series nonlinear changes,regional crust deformation characteristic analysis,seismic displacement field detection,and global plate motion model analysis.This paper mainly uses the 4-year data of Dali dense GPS network from 2018 to 2022,and conducts research through two parts: non-differential processing of conventional GPS data and double-differential processing of seismic high-rate GPS data,the former mainly to study the GPS time series analysis method and the deformation characteristics of the crust in the scope of the Yangbi earthquake in Dali,and the latter is to use the high-rate data of the earthquake to analyze the deformation characteristics of the land surface and compare the accuracy of different seismic time solving strategies.The main research contents are as follows:(1)In the data solving part,GIPSY software with precision single-point positioning mode is used to solve the conventional observation data of Dali dense GPS network from2018 to 2022,and QOCA is used to adjust to obtain the coordinate time series results of the station relative to ITRF 2014.(2)Three methods for analyzing GPS time series noise are introduced,and principal component analysis for extracting common-mode errors is introduced in detail.Then,the principle is used to extract the common-mode error from some stations of the Dali dense GPS network,and the contribution rate of each order principal component and the normalized spatial response of each order principal component are obtained during the processing process,and then the noise analysis is carried out before and after the common mode error is removed,the spectral index and maximum likelihood value of the noise sequence are calculated firstly,and then the maximum likelihood estimation value before and after the common mode error is eliminated to determine the optimal noise model of the Dali GPS network.(3)The TRACK module using dynamic differential positioning method according to the near-field 1Hz and 5Hz rates in the near-field area is used to obtain the complex time series of ground surface motion,which can better reflect the analysis results of high-rate GPS data on seismic dynamic displacement,and at the same time,the influence of different high-rate GPS dynamic data processing methods and different precision ephemeris on the seismic time accuracy is compared and analyzed by using different high-rate GPS dynamic data processing methods and different precision ephemeris to study the calculation accuracy of high-rate GPS during earthquake time.(4)The horizontal and vertical velocity fields of the earth’s crust and their strain background characteristics in this area before the Yangbi earthquake were studied.The results show that the velocity field can be accurately estimated by the dense GPS observation array observation data,and the overall motion speed of the Dali area where the array is located increases from north to south and from west to east.Under the combined action of eastward escape of the Qinghai-Tibet Plateau and wedge of Sichuan-Yunnan diamondshaped block,the east-west velocity of the Weixi-Qiaohou-Weishan secondary fault changed in the east-west direction,showing the characteristics of right-handed walk-slip.The strain rate field can have an intuitive reflection of the deformation of the earth’s crust,×and the highest value of the principal strain rate is 8.98×10-8/a,the highest value of the surface expansion rate is 2.55×10-7/a,and the maximum value of the maximum shear strain rate is2.98×10-7/a.The strain rate parameter can accurately indicate a condition in the seismic area of the Yangbi earthquake,which is located in the horizontal movement retardation zone of the earth’s crust,and the rapid accumulation point of strain,that is,the high value area of the surface expansion rate and the maximum shear strain rate. |
