汶川地区夏季电离层VLF背景分析  

Summer's ionosphere VLF background analysis in Wenchuan area

作　　者：杨静[1] 胡耀垓[1] 赵正予[1] YANG Jing;HU YaoGai;ZHAO ZhengYu(Ionosphere Laboratory of Wuhan University,Chinese Academy of Sciences,Wuhan 430072,China)

机构地区：[1]武汉大学电离层实验室,武汉430072

出　　处：《地球物理学进展》2021年第2期531-539,共9页Progress in Geophysics

摘　　要：西南地区是我国地震灾害频发的区域,本文以汶川(31.0°N,103.4°E)为例,运用了空间网络化的方法对DEMETER卫星2005—2007年三年的5、6、7、8月的夏季电离层低频电场数据进行时空规律分析.通过将卫星接收到电场信号分为SLF、ULF、VLF和LF四个频段,研究了以汶川为中心纬度为21.0°~41.0°N、经度为90.0°~110.0°E范围内的电离层电场背景场的时空分布规律.本文首次研究汶川区域夏季电离层VLF规律,在探讨了电离层VLF多频段电场背景特征的基础上,从时空分布规律上寻找、确定了地震前后造成的电离层多频段电场的异常现象.结果表明:(1)夏季中国西南汶川地区不同年份的相同月份、相同频段的背景功率谱密度变化范围较为一致.(2)与2008年5·12汶川地震前后电场数据进行对比分析,发现地震前后电离层的各个频段均出现了电场功率谱密度的高于背景电场功率谱密度的异常增强,其中震前电离层在VLF、LF频段会出现明显的电场功率谱密度超过3σ增强的现象,增强会达到2.5个数量级.Southwest China is a region with frequent earthquake disasters in China.This article takes Wenchuan(location coordinates 31.0°N,103.4°E)as an example,the regularity statistics of ionospheric background electric field in the the VLF band are studied,which the latitude range from 21.0°N to 41.0°N and the longitude range from 90.0°E to 110.0°E.This study does the statistical analysis with the VLF electric field waveform data,and the data from 2005's summer and 2007's summer which is got from the DEMETER satellite.In this article,Summer refer to May,June,July and August.The study is committed to researching the VLF frequency band law of the ionosphere in the Wenchuan region.According to background characteristics of multi-band electric field in ionospheric VLF,we has found there was an unusual phenomenon that ionospheric electric field abnormally increased before and after earthquake.The study shows that(1)the Wenchuan's background Power Spectral Density(PSD)of the same month in different years is nearly consistent,and so is the PSD of the different frequency.(2)The electric field PSD at night is consistent in the four frequency bands'value.The electric field diurnal PSD has the phenomenon of the first frequency band>the second frequency band>the third frequency band≈the fourth frequency band.The diurnal PSD of the first frequency band is 1~2(lgμV2m-2Hz-2)larger than that of other frequency bands.After comparing with the Wenchuan earthquake case in May 12th 2008,it is found that the VLF band of the ionosphere will have an abnormality that the electric field PSD is 2.5 times higher than the background electric field PSD before and after the earthquake.And the highest increase is more than 3σ.

关 键 词：DEMETER卫星 低频电场 电场功率谱密度 地震 

分 类 号：P352[天文地球—空间物理学]