| The rapid development of satellite seismic observation technology has provided new research tools and data for seismologists in various countries.Although scholars have discovered the large number of seismic ionospheric effects recorded by electromagnetic satellites,earthquake prediction remains a major challenge today due to the complexity of seismic breeding mechanisms.Southwest China and Japan are regions or countries with frequent seismic hazards in Asia.If the possible seismic ionospheric effects can be explored and summarized,more information and methods can be provided for their seismic ionospheric coupling mechanisms and earthquake prediction.In this paper,the spatially networked method is used to analyze the spatio-temporal laws of the summer ionospheric low-frequency electric field data and plasma data of the DEMETER satellite in May,June,July and August for the three years from 2005 to 2007,using the Southwest China and Japan regions as examples.The spatio-temporal distribution laws of the ionospheric electric field background field in the southwestern seismic region of China and Japan were studied by dividing the satellite received electric field signals into four frequency bands: SLF,ULF,VLF and LF.In this paper,we study for the first time the summer ionospheric VLF and plasma laws in southwestern China and Japan.Based on the background characteristics of the ionospheric VLF multi-band electric field and plasma,we search for and determine the anomalies of the ionospheric multi-band electric field before and after earthquakes from the spatio-temporal distribution laws.The main work of the paper is as follows.1.After determining the study scope of the southwest China and Japan regions,the data of the selected regions in 2005-2007 were analyzed and statistically analyzed in the summer background using the low-frequency electric field and plasma of the ionosphere as indicators and the networked data analysis method to provide scientific background information for the analysis of specific seismic cases.2.The Wenchuan earthquake and the four Japanese earthquakes were selected as examples,and the same method was used to perform multi-band spatio-temporal analysis of the low-frequency electric field and plasma analysis for the five examples.The analysis found that:(1)five cases showed significant enhancement of the ionospheric electric field power spectral density in multiple frequency bands before and after the earthquake,with the most significant enhancement in the VLF and LF bands.(2)The location of the VLF band anomalies is different for different seismic cases due to different seismic incubation mechanisms.(3)Only two of the five seismic cases had plasma anomalies before and after the earthquake. |
