| Satellite technology can provide a wealth of information on earthquake precursors for it has wide coverage, large amount of information, good dynamic and high resolution. Now, China arthquake lectromagnetic atellite project has been officially included in the national plans of satellite launch. Based on observation satellite and , we can build a united observational system identify and extract informationelectromagnetic, ionosphere and high-energy particle to earthquake precursors and realize large-scale and continuous spatio-temporal observation of earthquake electromagnetic information for and surrounding areas. And it can improve the scientific level for earthquake forecastthe ability for short-term prediction and can provide the basis of breakthrough for earthquake forecast.Ionospheric research for seismic analysis in China has just started, and seismic anomaly extractions need more information to determine and validate. The seismo-ionospheric effect is not only observed by satellite technology, but also by effective ground observation technology. Using the existing satellite data and ground observation data to research the seismo-ionospheric effects and summarizing the law of seismo-ionospheric effect is one of the necessarily preparatory work.According to the development of three dimension electro-magnetic observation system for earthquake, in this thesis, researches on the abnormal characteristic of TEC of seism based on the observation system of GPS have been done. The aim of this study is to promote the electro-magnetic satellite project. Based on the GPS data of Crustal Movement Observation Network of China and the TEC Map data provided by JPL, seismo-ionospheric effect is also investigated. In this work, ionospheric TEC abnormal test methods at home and abroad are reviewed and optimized. Several methods, such as TEC abnormal signal detection and analysis of TEC disturbance filter, are advanced to test seismp-ionospheric TEC anomaly. Using these methods, we make a statistical analysis of earthquake cases on the basis of M≥6 earthquakes occurred after 2000 in China, and summarize ionospheric abnormal characteristics before strong earthquakes to provide support for the application of ionospheric monitoring methods in earthquake prediction. In order to research the ionospheric abnormal characteristic with ground GPS, the data of COSMIC and f0F2 are analyzed to examine the ionospheric disturbance before earthquake.Firstly, earthquake and its causes, the ionosphere and ionospheric disturbance are introduced; the research status of seismo-ionospheric effect at home and abroad are investigated; the case studies and statistics studies about seismo-ionospheric effect at are reviewed; the mechanisms of the seismo-ionosphere coupling are also introduced.Secondly, the basic situation of GPS system, including GPS signal, GPS observables and the observation equations, and GPS signal propagation delay in the ionosphere are introduced. We focus the principles and methods of calculating TEC using the GPS data, and discuss the method and corresponding algorithms in detail using the Dual-frequency GPS.Then, several test method in TEC disturbance are discussed and optimized, and some methods to test TEC anomaly are proposed as follows:(1) Optimization of the envelope method. We make the smoothing TEC median value before 15 days as the reference values, the smooth interquartile range as abnormal detection bound, and it contributes to scientific research of the relationship between the ionospheric TEC disturbance before the earthquake and the earthquake preparation.(2) Combination of Neyman-Pearson test in signal processing and hypothesis testing in statistics. To test the possibility of the TEC anomaly before the earthquake, we use two mathematical methods in different subject to make a preliminary quantitative analysis.(3) Study in detail TEC change between a single GPS satellite and GPS station, and filter the TEC change from observations of each GPS satellite and station.(4) Study the seismo-ionospheric effect from a variety of ionospheric parameters. It can provide the reference basis for ionospheric TEC anomalies of seismic testing through the comparative study of ground GPS, COSMIC and foF2 probed by the ionosondes.By taking the Wenchuan earthquake as an example, the method for testing ionospheric TEC disturbance before and after the earthquakes have been used and following results are obtained.(1) Significant positive TEC anomalies appeared at GPS reference stations near the epicenter on May 3 and May 9 before the Wenchuan earthquake. Excluding the influence of factors from the space, TEC anomalies on May 9, 3 days before the earthquake show close correlation with the Wenchuan earthquake.(2) Analysis on the spatial distribution of TEC shows that the area of the TEC anomalies before the earthquakes did not appear right above the epicenter, but above the area south east to the epicenter. The global distribution of DTEC shows that the area of the TEC anomalies above Chinese mainland appeared only near the epicenter and there was a conjugate form for positive anomalies appeared 3 days before the earthquake.Based on 33 earthquakesoccurr in China we study the effect of ionosphere and summarize the characters of TEC abnormal before big earthquake. The statistical results are as follows:(1) The TEC abnormal usually appears several days before earthquake and discontinuous and lasts few hours each day except for some strong earthquake. The TEC abnormal associated with local time at epicenter.(2) The TEC variations can have a positive or negative sign. The relative magnitudes of the TEC anomalies were in the range of 20%～30%, but may be larger than 100% at certain time before individual large earthquakes.(3) The areas of the TEC anomalies before the earthquakes did not always appear above the epicenters, they may shift towards the equator. Ionospheric disturbances may appear in the conjugate area of the earthquake epicenter along the magnetic lines. A variety of ionospheric parameters have similar changes with TEC. |
PDF Full Text Request