Key Techniques On Deriving Geodetic Crustal Movement Velocity Field In Continental China

GPS has the advantages of all-weather,large scale,high precision,and high time resolution,and is one of the important means of monitoring crustal deformation.In the past three decades,GPS has played an important role in the study of crustal deformation in continental China.However,there are still many problems in the solution of the GPS velocity field in continental China,such as the detection and elimination of gross errors in GPS coordinate time series,periodic deformation estimation,common mode error,coseismic step and post-seismic deformation caused by large earthquakes,velocity Accurate estimation of uncertainty,etc.Whether these problems are solved is related to the accuracy of the long-term GPS velocity field,and has an important impact on the analysis of crustal movement characteristics.In order to obtain the highest-resolution GPS velocity field in continental China today,this thesis collects,organizes and processes the GPS observation data of the China Crustal Movement Observation Network Of China and multiple projects in Sichuan and Yunnan from 1998 to 2021,and comprehensively uses the trajectory model.And independent component analysis,and solve various problems existing in GPS coordinate time series through a series of space-time seismic models,and solve the crustal velocity field of Chinese mainland.On this basis,the strain rate field of the crustal movement in the Chinese continent is calculated,the slip rate and the locking depth of the active faults are calculated,and the characteristics of the crustal movement in the Chinese continent are analyzed.The main research results and conclusions of this thesis are as follows:(1)Process the GPS observation data of the China Crustal Movement Observation Network Of China and the stations built by some projects in the Sichuan-Yunnan region,solve the single-day solutions of all GPS stations under the ITRF2014 framework,and convert the geocentric coordinates XYZ to the station center Coordinate ENU,get high-precision GPS coordinate time series.The initial processing of GPS coordinate time series is carried out by comprehensive use of trajectory model fitting and independent component analysis method,and the step,gross error,seasonal deformation and common mode error caused by antenna variation in GPS coordinate time series are corrected.Different processing strategies are adopted for different earthquakes: for the rover,the coseismic step of the continuous station is used to perform spatial interpolation to improve the coseismic deformation of the rover;The GPS coordinate time series without pre-earthquake observations but affected by the afterearthquake is corrected by the method of spatial interpolation of post-earthquake amplitude.By subtracting the velocity of the Eurasian plate from the Euler vector,2462 GPS station velocities under the Eurasian frame are obtained,and the published GPS velocity fields in continental China and its surrounding areas are combined to finally obtain a total of 3812 measurements under the current Eurasian frame.Station's GPS velocity field.(2)The GPS coordinate time series presents different noise characteristics in the E,N and U directions.The main noise model of GPS coordinate time series in continental China is white noise plus flicker noise.There are large differences in velocity uncertainty calculated using different noise models.In the east,north and vertical directions,the velocity uncertainty calculated by the optimal noise model is(11.5±2.1)times,(12.9±2.9)times and(14.8±3.7)times that of the white noise model only.There is little difference between the velocity calculated by the maximum likelihood estimation method and the FOGMEX method,and the velocity uncertainty calculated by the maximum likelihood estimation method is(2.8±1.5)times and(1.5±0.7)times that of the FOGMEX method,respectively.and(3.5±2.8)times.(3)Based on the GPS velocity field,the principal strain rate field,the second invariant field of the strain rate tensor,the maximum shear strain rate field and the surface expansion strain rate field in continental China are calculated.The results show that the strain rates in different regions of continental China have different characteristics.High strain rates are mainly distributed at the plate junction and some active faults,including the Eurasian-Indian plate junction,the Tianshan Mountains,the Kunlun Mountains,the Xianshuihe-Xiaojiang fault,For the Altyn fault,the strain rates in these regions are all above 40nstrain/yr,while the Qinghai-Tibet Plateau and the Zhangjiakou-Bohai Sea seismic zone in the North China Plain have extensive diffuse deformation with a strain rate of about 20nstrain/yr.The Qinghai-Tibet Plateau has extensive surface expansion,and the expansion rate is about 10-20 nstrain/yr.(4)The slip rates and locking depths of major faults are inverted according to the GPS velocity profile.It is concluded that the slip rates of the Tanlu fault,the western segment of the Altun fault,the northern segment and the middle segment of the Karakoram fault are all lower than 1 mm/yr;There is a right-lateral strike-slip of 3.1 mm/yr in the middle section of the Altun fault;the left-lateral slip rate in the middle section of the Altun fault is 8-10 mm/yr,and the locking depth is 17.3-23 km,and the left-handed slip rate in the eastern section decreases to 5.4 mm/yr,and the locking depth is 13.5km;the Xianshuihe-Xiaojiang fault is a left-lateral strike-slip,the slip rate is 6.6?9mm/yr,and the locking depth is 9?19.2km.