Research On Pre-Seismic Feature Recognition Of Spatial Electric Field Data Recorded By CSES

A large number of studies have shown that low-frequency electromagnetic radiation will be generated in the process of earthquake breeding,thus releasing electromagnetic signals that can be captured.This phenomenon on the ground is manifested as abnormal sudden change in the intensity of the geomagnetic field,and abnormal charge in the cracks of the rock mass observed by the geoelectric field.The ionosphere is characterized by fluctuations of parameters such as electricity,magnetic field radiation,ionospheric electron density,and high-energy particles,which are often characterized by abnormal changes in parameter data within fifteen days before the earthquake.In order to study the abnormal disturbance of the ionosphere in space caused by strong earthquakes and further explore the precursory information of ionospheric earthquakes,based on the introduction of the ZH-1 satellite payload,this paper studies the applicable scope and advantages of different data processing methods,and proposes a comprehensive processing electric field.The algorithm of ULF frequency band data has formed a set of relatively standardized procedures for comprehensively processing satellite data,and applied to the analysis of two shallow earthquakes,and obtained satisfactory results.The main research contents and research results of the paper are as follows:(1)On the basis of studying various time-frequency signal analysis methods,the applicable scope and advantages of different data processing methods are summarized,and an algorithm based on S-G filtering,wavelet transform and empirical mode decomposition and reconstruction is proposed which named SG-WT-EMD(Savitzky-Golay ? Wavelet Transform ? Empirical Mode Decomposition)algorithm.The algorithm not only includes time domain filtering,time series anomaly detection,time-frequency domain conversion,but also includes signal decomposition and reconstruction,forming a set of relatively standardized procedures for processing space electric field data,which improves the accuracy of data analysis,which provides a new reference method for scientific research such as space electric field waveform data.(2)Using the SG-WT-EMD algorithm,based on the ULF band waveform electric field Ex,Ey,and Ez three-component data recorded by the ZH-1 satellite,the disturbance before the M7.7 earthquake in the southern waters of Cuba and the southern waters of Sumatra,Indonesia was studied.On the basis of removing the influence of space weather activities,the revisited orbit data in multiple periods before the earthquake were analyzed.In the application of the SG-WT-EMD algorithm,the S-G filtering method is used to extract small-scale waveforms conventionally,and then the wavelet time-frequency analysis is used for feature extraction,and then the EMD empirical mode decomposition method is used to analyze the disturbance features,which achieves the purpose of effectively extracting the spatial electric field disturbance features before the earthquake.(3)The analysis results of earthquake cases in the southern waters of Cuba show that: in terms of time,there were large anomalies from 15 days before the earthquake,and the disturbance changes of some orbits continued to five days after the earthquake;in terms of location,the main disturbance changes concentrated over the epicenter area,with fewer conjugate areas;in terms of amplitude,in the five days before the imminent earthquake,the disturbance of most orbits exceeded the threshold value of the background value,and some orbits were smaller than the threshold value;in terms of shape,there were fluctuations that did not exceed the threshold value It appeared on the south side of the epicenter,and some appeared on the north side.(4)The analysis results of the earthquake cases in the southern sea area of Sumatra Island show that in the fifteen days before the earthquake,there were abnormal changes in the south of the equator in most orbit data,and the pre-e arthquake signal disturbance changes in a few orbits were different from the b ackground values.The innovation of this article:(1)An SG-WT-EMD comprehensive processing algorithm suitable for satellite electric field data is proposed,and a set of relatively standardized procedures for processing space electric field data is formed.The algorithm not only includes time domain filtering,time series anomaly detection,time-frequency domain conversion,but also signal decomposition and reconstruction,which improves the accuracy of data analysis and provides a new reference for scientific research such as space electric field waveform data.method.(2)Using the SG-WT-EMD algorithm,the earthquake in the southern seas of Cuba and the southern sea of Sumatra,Indonesia were analyzed for the first time.The calculation results found that the electric field data in the time evolution of multiple revisited orbits,the signal changes in the epicenter area and the conjugate area are consistent.When the north-south region of the epicenter has a large disturbance,its conjugate region also has similar fluctuation changes.