There are a number of ionospheric models available for research and application, such as the polynomial model, generalized trigonometric series function model, low degree spherical harmonic function model, adjusted spherical harmonic function model, and spherical cap harmonic function analysis. Using observations from more than 40 continuously operating stations across Antarctica in 2010, five models are compared with regard to their precision and applicability to polar regions. The results show that all the models perform well in Antarctica with 0.1 TECU of residual mean value and 2 TECU of root mean square error.
We process the standard 30 s,static GPS data and the 1 s,high-rate GPS(HRGPS)data provided by the Crustal Movement Observation Network of China with GAMIT/GLOBK software package,and obtain the coseismic displacements of near field and far field,and the epoch-by-epoch time series of HRGPS during Lushan earthquake.GPS data from about 20 sites in Sichuan province,which located between 40 and 450 km from the epicenter,are analyzed so as to study the characteristics of the static displacements and the dynamic crustal deformations,with periods ranging from several minutes to over a month.The result shows that:the static displacements caused by Lushan earthquake are limited to several centimeters;the nearest station SCTQ at 43 km from the epicenter has the largest static displacement of about 2 cm,while the other stations generally have insignificant displacements of less than 5 mm.the stations in the east ofSichuan–Yunnan region shifts 5–10 mm toward the southwest,and the stations in the middle-west of Sichuan Basin moves indistinctively 1–2 mm toward the northwest;station SCTQ has the largest kinematic displacement of about 4 and 3 cm peak-to-peak on the north and east component,respectively,and is much greater than the static permanent displacement;for the stations located at a distance greater than 150 km from the epicenter,the kinematic motions are generally insignificant;exceptionally,station SCNC and station SCSN in central Sichuan Basin have significant kinematic motions although they are more than 200 km away from the epicenter.
Yujun DuZemin WangShujiang YangJiachun AnQiang LiuGuowei Che
