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Is the strengthened spectrum at cut-off frequency in daytime electromagnetic field a precursor of strong earthquakes?

机译:白天电磁场中截止频率处的增强频谱是否是强烈地震的先兆?

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摘要

Based on two case studies recorded by DEMETER satellite in 2006 and long time series comparison, some increases and decreases in electric field power spectra were revealed before two strong earthquakes. We focus on the electromagnetic field spectra at 300-500Hz around cut-off frequency during local daytime. The results show that, compared with the normal background, the electromagnetic emissions decreased at ionospheric altitude(660km) in a month before thernevents, and there are a few days with electric field spectra increasing, larger than 10~(15) μV~2 /m~2 / Hz . In order to getrnmore reliable results in anomaly extracting, the study of temporal evolutions of electromagnetic emission at cut-off frequency, as well as monthly and seasonal variations should be studied, besides the short time behaviors. Finally the mechanism of long time variations in electromagnetic field in ionosphere was discussed.
机译:根据DEMETER卫星在2006年记录的两个案例研究以及长时间序列比较,在两次强地震之前,发现了电场功率谱的一些增加和减少。我们关注本地白天在截止频率附近的300-500Hz的电磁场频谱。结果表明,与正常背景相比,电离层在事件发生前一个月(660km)的电磁辐射降低,并且有几天的电场谱增加,大于10〜(15)μV〜2 /。 m〜2 /赫兹为了在异常提取中获得更可靠的结果,除了短时行为外,还应研究截止频率下电磁辐射的时间演变以及月度和季节变化。最后讨论了电离层电磁场长时间变化的机理。

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