Evaluation of vertical crustal movements and sea level changes around Greenland from GPS and tide gauge observations

To better monitor the vertical crustal movements and sea level changes around Greenland,multiple data sources were used in this paper,including global positioning system(GPS),tide gauge,satellite gravimetry,satellite altimetry,glacial isostatic adjustment(GIA).First,the observations of more than 50 GPS stations from the international GNSS service(IGS)and Greenland network(GNET)in 2007–2018 were processed and the common mode error(CME)was eliminated with using the principal component analysis(PCA).The results show that all GPS stations show an uplift trend and the stations in southern Greenland have a higher vertical speed.Second,by deducting the influence of GIA,the impact of current Gr IS mass changes on GPS stations was analysed,and the GIA-corrected vertical velocity of the GPS is in good agreement with the vertical velocity obtained by gravity recovery and climate experiment(GRACE).Third,the absolute sea level change around Greenland at 4 gauge stations was obtained by combining relative sea level derived from tide gauge observations and crustal uplift rates derived from GPS observations,and was validated by sea level products of satellite altimetry.The results show that although the mass loss of Gr IS can cause considerable global sea level rise,eustatic movements along the coasts of Greenland are quite complex under different mechanisms of sea level changes.

Preliminary division of active block boundary in Chinese mainland based on recent vertical crustal movement

The characteristics of vertical crustal movement in Chinese mainland are studied, and the ideas and principles for dividing active blocks according to the map of recent vertical crustal deformation rate in China is proposed. As a result, Chinese mainland is divided into 2 first-grade blocks, the east and west block, 6 second-grade blocks, the Northeast China, North China, East China, Xizang (Tibet), Gansu-Qinghai-Xizang (Gan-Qing-Zang) and Xinjiang block, and 16 third-grade blocks. The boundaries of active blocks divided in this paper are generally consistent with the pattern of neotectonic movement with some local difference. It shows that the recent crustal activity in Chinese mainland inherits the neotectonic movement occurred since the Quaternary, while some new activity tendencies appear.

Vertical deformation analysis based on combined adjustment for GNSS and leveling data

A method is proposed to fuse the velocity data of the global navigation satellite system(GNSS) and leveling height via combined adjustment with constraints. First, stable GNSS-leveling points are uniformly selected, and the constraints of the geodetic height change velocity and normal height change velocity are given. Then, the GNSS vertical velocities and leveling height difference are used as observations of combined adjustment, and robust least-squares estimation are used to estimate the velocities of the unknown points. Finally, a vertical movement model is established with the GNSS vertical velocities and leveling vertical velocities obtained via combined adjustment. Data from the second-order leveling network and GNSS control points in Shandong Province are taken as test data, and eight calculation schemes are used for discussion. One of the schemes, the bifactor robust combined adjustment method based on variance component estimation with two kinds of vertical velocity constraints achieves the optimal results. The method applied in the scheme can be recommended for data fusion of GNSS and leveling, further improving the reliability of vertical crustal movement in Shandong Province.

Present three-dimensional crustal deformation in Hainan Island

Hainan Island,located at the southeast edge of the Eurasian Plate,is affected by the motion of multiple plates,with its northeast edge mainly dilatating and its western margin presently compressing. By analyzing the GPS rates during 1999- 2007 in Hainan and its adjacent region,we determined horizontal movement rates of 3. 0-21. 1 mm /a at the west of 104°E,evidently affected by the Indian Plate extrusion.Their directions are SE-SN-SW from east to west and are separated by the main fault. The principal strains have the same characteristics. The stations east of 104°E move mainly in the SEE direction. The eastward rates are 2. 1-8. 5 mm /a and northward rates are 0. 4- 2. 7 mm /a. The GPS rates during 2009- 2013 show that stations at the edge of the island move SEE relative to the Eurasian Plate,with rates relative to the mean benchmark,indicating that there are small relative movements between stations,whereas QION station,located in the middle,moves in the NW direction at a greater rate. Vertical differential movement is apparent in the northeast zone of the island. Upwelling of mantle plume material possibly influences the local stress.Three-dimensional GPS rates indicate that,at present,inherited crustal movement is dominant in Hainan.

Tests of relative vertical offsets for several types of GPS receiver antenna phase centers

The correction for antenna phase center is considered in processing Global Positioning System （GPS） data collected from a network of GPS ultra-short baselines. Compared with the leveling measurements, the GPS results show that the relative vertical offsets for the pairs of GPS receiver antenna phase centers still exist, although absolute calibration of the antenna phase center variations （PCVs） has been considered. With respect to the TPS CR.G3 antenna, the relative vertical offset for the LEI AT504 antenna is 8.4 mm, the offset for the ASH701945C_M antenna is 5.5 mm, and those for the ASHY00936E_C and ASH701945B_M antennas are approximately between 2 mm and -3 mm. The relative offsets for the same type of antennas are approximately 1 mm. By correcting the absolute PCVs, the existing relative offset becomes negligible for horizontal positioning.