Study On High-rate Epoch By Epoch GPS Positioning And Its Application In Seismology

The object of this thesis is to study the implication of High-rate GPS data in seismology. First, 1-Hz GPS data processing method was researched, and then using 1-Hz GPS receiver as one-second sampling rate displacement meter researched kinematics ground deformation caused by earthquake. With single epoch positioning module Track in GAMIT, the basic theories on 1-Hz GPS data processing was studied, involving discrete Kalman filtering in single epoch GPS positioning, ambiguity resolution in Track. The source code of Track was read,and, observed GPS data was processed by Track.The single epoch GPS positioning precision was evaluated. The 1-Hz GPS positioning precision is influenced by some noise. According to the different characteristics of the error, two filtering methods were designed to improve 1-Hz GPS positioning. For static GPS data, the 1-Hz GPS positioning precision was obtained through the analysis of the discreteness of position sequence. When base line within 100km, the positioning precision is 5-6mm in horizontal direction, and in vertical direction, the precision is 3 to 4 times than the former.Spatial filtering was studied in the thesis. At a GPS observation network to teleseismic distance, spatial filtering could obtain estimates of the absolute of the reference station plus the GPS common mode noise. We also showed 1-Hz GPS displacement time series can be used to produce surface wave information that compare very well with those produced by near broadband seismometers, which verified the accuracy of the reference displacement.We obtained near-field ground motions and far-field surface wave information at Wenchuan earthquake using 1-Hz GPS data, and gave a brief analysis for those results. Through the analysis of 1-Hz GPS data observed at 13 GPS stations near the epicenter, we investigated ground deformation caused by this large earthquake. Results show that 1 Hz GPS observations clearly captured the kinematic ground displacements of the main shock. The characteristics of 1-Hz GPS displacements suggest that two factors control the ground deformation: one is the distance between the GPS station and the epicenter of the main shock, the other is the distance between GPS stations and the rupture zone. For PIXI station, the nearest one to the epicenter, its maximal kinematic displacements exceeded 0.7m along the north-south direction, which exceeded 1.0m along the east-west direction. 1-Hz GPS displacements of PIXI GPS stations are in good agreement with the twice integral of strong motion data.Based on 1-Hz GPS data, the surface wave information aroused by Wenchuan Earthquake in Tianjin area was studied in the paper. Absolute displacement of the reference station was obtained by spatial filtering. Comparison between the 1-Hz GPS data analysis results and displacement seismograms integrated from seismometer showed a good agreement. 1-Hz GPS data clearly captured surface wave information in Tianjin region related to Wenchuan earthquake. Finally,1-Hz GPS Displacement Time Series Model was summarized in this thesis.