Study on Methods for Extracting Earthquake-related Anomalies Using Observations of DEMETER Satellite Illustrated by the Case of Pu’er
|School||China Seismological Bureau, Institute of Earthquake Prediction|
|Keywords||Pu'er earthquake DEMETER satellite Electron density Electron temperature Electric field spectrum Seismic anomaly|
China is an earthquake country, and the current earthquake prediction is still in the exploratory stage, earthquake monitoring and prediction is still a worldwide scientific challenges. The development of new means of observation, to extract seismic anomalies provide more comprehensive set of observations, which provide support for earthquake prediction research. The the satellite electromagnetic detection technology are emerging, data extraction earthquake ionospheric precursors has also become more and more attention in the new method of earthquake prediction research. Based on the actual needs of the Chinese earthquake electromagnetic test satellite project, and take full advantage of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite for four years to get observational data of seismic ionospheric effects, gain experience, lessons learned, for the China Earthquake electromagnetic satellite data processing work to lay the foundation. Research thesis research at home and abroad earthquake ionospheric effects, a review the case of the foreign research done in the earthquake ionospheric effects the shock case studies and statistical research; summarizes the course of development of seismic electromagnetic satellite and main stage; and introduced earthquake ionosphere coupling mechanism. In addition, the paper also gives the earthquake ionospheric anomalies of all kinds of characteristics are summarized in the previous studies, summarized earthquake examples of the Review of the performance characteristics of the abnormal. DEMETER satellite, including load and output data and products. Focus on applied seismic research progress, made a detailed report of the 2006 the DEMETER international seminar on its data processing and applications research and made presentations addition of unique reports in the literature. To the Pu'er earthquake, for example, explore the the DEMETER satellite observation data Seismic Research. The papers follow two images preliminary interpreted → 1 data in-depth analysis of the ideas. Through the initial interpreted, drawn up in, and to track down the different performance characteristics, found disturbance vast majority occur in liters rail track (that night when the place). Pick up in two disturbances abnormal and a no abnormal upward trend, together with a selection of an abnormal drop rail comparative study. With one year follow revisit orbit of VLF electric field measured spectral data measured electron density (Ne) and the electron temperature (Te), the electric field detector (ICE) of a Langmuir probe (ISL). Finally, summarizes the background characteristics and anomalies exhibited by the electron density, electron temperature and electric field spectrum three kinds of parameters, and the inadequacies of the thesis and future needs in-depth study of the problem. The papers made major progress and preliminary results are as follows: a research method is based on an observation of DEMETER satellite data, this paper explores several data processing and anomaly extraction method, and achieved good results are summarized as follows: (1) revisit orbit contrast Methods: According to the the DEMETER satellite orbit design features, will be every 16 days of track contrast, although the interval is relatively long, but this method can ensure that the contrast of the observation data of the satellites at the same position, is equivalent to removing the spatial variation. Provides an effective method for research background information. By contrast, more conducive to information found weak before the earthquake ionospheric disturbances. (2) the correlation analysis of the different parameters: by analyzing changes in the electron density and electron temperature curve and found that the relationship between them. Preliminary studies suggest that a positive correlation between them in the local area, but before the earthquake in a certain area, the performance of a negative correlation. The advantage of this method may be able to extract the potential exception. (3) the spatial and temporal evolution of image contrast: before the earthquake to the post-earthquake period of time, within a certain area of ??the satellite observation data contrast image of the temporal evolution of the parameters, to facilitate the analysis of changes in process before the earthquake ionospheric disturbances. (4) the electric field single-frequency information extraction method: extracted from the data of multiple electric field spectrum at a fixed frequency curve, easy prominent band of abnormal signal analysis before the earthquake. Pu'er earthquake ionospheric disturbances characteristic Pu'er earthquake, the two images are initially interpreted → 1 data in-depth analysis of research ideas. Exception information is extracted by analyzing the variation of electron density, electron temperature, electric field spectrum background and obtained the following understanding: (1) through the the Pu'er region ionospheric electron density (Ne) revisit orbit comparative analysis found that the ionospheric Ne background The field has obvious seasonal, day and night, and regional differences. Night Ne change morphology are mainly three types, that is a single peak, saddle and flat shape; different variation in four seasons: winter Southern Hemisphere Ne overall higher peak distribution of low latitudes in the southern hemisphere; spring and autumn. symmetric shape; Northern Hemisphere as a whole Ne high summer peak generally migrate to about 20 ° N. Ne in the change in the overall morphology of the four seasons during the day is very similar to the peak position in the near 10 ° N, the size of the peak is also very close. The daytime average electron density as a whole is higher than at night. Revisit orbit data comparison method to get the obvious precursor anomaly, nine days before the earthquake abnormal increase of about 77%, but may contain some changes in the background information, incomplete anomalies caused by the earthquake, and revisit the track The comparison of the data can provide the basis of a certain background. anomaly extraction Pu'er earthquake before the DEMETER satellite records uptrend disturbances significantly better than the drop rail proved ionospheric plasma disturbances discontinuous characteristics of the sub-periods, and the morning session perturbation signal is not obvious. (2) before the earthquake two months of the electron density (Ne) space image reflects a seismic anomaly before the earthquake a month or so began to render high-value anomalies the largest Impending before 10 days, 10-20 days before the earthquake in the epicenter The abnormal area there is a certain drift, and the magnitude weaken abnormalities disappeared after the earthquake. (3) the use of an electric field single frequency information extraction methods, found that before the earthquake anomalies concentrated in the band below 200Hz high band anomaly is not obvious. 40Hz electric field before the earthquake spectrum of spatial and temporal evolution chart reflects the four days before the earthquake near the epicenter of the night spectrum value abnormal enhancement phenomenon began to appear, two days before the earthquake anomalies more concentrated, abnormal disappeared after the earthquake. (4) the use of the method of correlation analysis of the electron density (Ne) and electron temperature (Te), six hours before the earthquake epicenter latitude 10 ° north area of ??a track between Ne and Te unusually strong negative correlation coefficient . This anomaly in time and space with the Pu'er earthquake corresponding good derived from the earthquake is likely exception. (5) In this study, the results obtained with contrast with previous findings, including abnormal parameters, abnormal, abnormal position and abnormal amplitude.