Study On Methods For Extracting Earthquake-related Anomalies Using Observations Of DEMETER Satellite Illustrated By The Case Of Pu'er

Numerous earthquakes have occurred in China. Meanwhile, earthquake prediction is still in the exploration stage at present. Earthquake monitoring and prediction are world-wide scientific problems all the same. To develop new techniques of observation can obtain more comprehensive data for extracting earthquake-related anomalies, so as to provide support for promoting earthquake prediction research. Satellite electromagnetic detection techniques spring up increasingly, and extracting seismo-ionospheric precursors from satellite data draws more and more attention. It becomes a new way in the earthquake prediction research.This paper is based on actual needs of the project named China Seismo-electromagnetic test Satellite. To study on seismo-ionospheric effect by making full use of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite observations in the past more than four years can sum up experience and lessons for laying the foundation of satellite data processing in future.First of all, we investigate the research status of seismo-ionospheric effects at home and abroad. We introduce the mechanism of the seismo-ionosphere coupling; review the case studies and statistics studies about seismo-ionospheric effect abroad; and sum up the history and the main stages of the development of seismo-electromagnetic satellite. In addition, the paper gives the various characteristics of seismo-ionospheric anomalies summarized by previous research. And according to case studies reviewed, we also generalize the features of seimo-ionospheric anomalies.Secondly, we introduce the basic situation of DEMETER satellite, including its payloads, data and products. And we focus its applied research progress. We investigate the report of data processing and application on the 2006 international conference of DEMETER satellite in detail, and give a presentation of relevant typical research in literature.Then, we study on Pu'er earthquake using DEMETER satellite observations. The thesis adopts the idea from preliminary interpretation of level-2 images to in-depth analysis of level-1 data. Through preliminary interpretation, we conclude different characteristics of ascending and descending orbits, and find that the majority of disturbances occurred in ascending orbits. We select two ascending half orbits with perturbations, one ascending and one descending half orbits without perturbation. For these four half orbits, we analyze the electron density (Ne), electron temperature (Te) and Power spectrum of the VLF Electric Field (VLFe"SP") data recorded in their revisited orbits during a year before Pu'er earthquake.Finally, we summarize background characteristics and anomalies of the electron density (Ne), electron temperature (Te) and Power spectrum of the VLF Electric Field (VLFe"SP"), and propose inadequacy of thesis and the problems which need be further studied.The major progress and preliminary results of this thesis include:1 Research methodsOn the basis of level-1 data observed by DEMETER satellite, we explore several methods achieving preferable results and summarize them as follows:(1) Comparison of revisited orbits: according to orbit designing features of DEMETER satellite, we compared the orbits every 16 days. Despite of long interval of time, this method can guarantee the comparison of the observations of satellite in the same location, the equivalent of excluding the impact of spatial changes. At the same time, it is easier to find the weak ionospheric disturbance information before earthquake by the comparison.(2) Relevant analyses of different parameters: we find the correlation between electron density (Ne) and electron temperature (Te) by analyzing their curves. On preliminary study, we consider they show a positive correlation in a local region, but they perform the negative correlation in certain area coverage before earthquake. This method can be used to extract information of potential anomalies.(3) Comparison of space-time evolution images: It is easier to analyze the variation process of ionospheric disturbances before earthquake by the comparison of the observations of satellite in a period time and certain area from pre-earthquake to post-earthquake and the extraction of the abnormal variations of them.(4) Extraction of single-frequency of Power spectrum of the VLF Electric Field (VLFe"SP"): It is facilitated to analyse the prominent single band of anomaly before earthquake by extracting single-frequency of power spectrum of VLF electric field.2 The features of seismo-ionospheric disturbances of Pu'er earthquakeWe adopt the idea from preliminary interpretation of level-2 images to in-depth analysis of level-1 data for Pu'er earthquake. Through analyzing the law of background variations of Ne, Te and VLFe"SP"and extracting earthquake-related anomalies, we have acquired information as follows.(1) Through the analysis of the characteristics of Ne, Te and VLFe"SP"in Pu'er region, we find that there are significant differences of the ionospheric background in season, day and night, and regions. There are three main types of Ne variations in night time: single-peak, saddle-shaped and even-shaped. There are different variation characteristics in four seasons also in night time: in winter, Ne of southern hemisphere is wholly higher whose peak distributes in the low-latitude of southern hemisphere. In spring and autumn, the shape of Ne is symmetrical whose peak distributes in northern hemisphere. In summer, Ne of northern hemisphere is wholly higher whose peak moves to about 20°N generally. At daytime, the whole variation shapes of Ne are similar in every season, and the peaks appear near 10°N around, whose values are also very similar.The average of Ne in daytime is higher than that of nighttime.We extract significant Ne precursors by comparison of the revisited orbits, finding the amplitude of anomaly increase to around 77%. But there may be certain background information, and it is not entirely caused by the earthquake. This method can provide a background basis for extracting anomalies. The disturbance of ascending orbits is superior to those of descending orbits recorded by DEMETER satellite. It can prove that ionospheric plasma disturbance appears discontinuously at times, and disturbed signal is not obvious during the morning.(2) Ne time-space images of two months before the earthquake show that a high-value anomaly begins to appear near the area of epicenter one month before the earthquake, and arrive at maximum 10-20 days before the earthquake, and there is a certain drift of abnormal region and weakened amplitude in impending 10 days. Anomalies disappear after the earthquake.(3) In addition, we find out abnormal enhancement of VLFe"SP"concentrate at frequency below 200Hz, and the anomaly is not obvious at high frequency. Temporal and spatial images of VLFe"SP"at 40Hz in 10 days before the earthquake show that abnormal enhancement begins from 4 days before and it is more focused before 2 days. Anomalies disappear after the earthquake.(4) Through the correlation analysis of Te and Ne, we find out the strong negative correlation characteristics between them in the region of 10°north of the epicenter recorded in a half orbit flying over the epicenter six hours before the earthquake. This anomaly corresponds well with Pu'er earthquake in terms of time and space, and it is likely to come from this earthquake.(5) The results of the thesis are comparable with those of previous studies, including parameters, time, location and amplitude of anomalies.