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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/angeo-2020-7
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-2020-7
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: regular paper 03 Mar 2020

Submitted as: regular paper | 03 Mar 2020

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A revised version of this preprint is currently under review for the journal ANGEO.

The VLF transmitters' radio wave anomalies related to 2010 Ms 7.1 Yushu earthquake observed by DEMETER satellite and the possible mechanism

Shufan Zhao1, Xuhui Shen1, Zeren Zhima1, and Chen Zhou2 Shufan Zhao et al.
  • 1Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
  • 2School of Electronic Information, Wuhan University, Wuhan, 430072, China

Abstract. Earthquakes may disturb the lower ionosphere through various coupling mechanisms during their seismogenic and coseismic periods. The VLF signal radiated from ground-based transmitters will get affected when it penetrates the disturbed region in the ionosphere above the epicenter area, and this anomaly can be recorded by low earth orbit satellite under certain conditions. In this paper, the temporal and spatial variation of the Signal to Noise Ratio (SNR) of the VLF transmitter signal in the ionosphere over the epicenter of 2010 Yushu Ms 7.1 earthquake in China is analyzed. The results show that the SNR over the epicenter of Yushu earthquake especially in the southwestern region decreased (or dropped)revealed by one satellite revisit period before the main shock, which is consistent with the observed TEC anomaly at same time, implying that the decrease of SNR might be caused by the enhancement of TEC. A full-wave method was used to study the mechanism of the change of SNR before the earthquake. When the electron density in the lower ionosphere increases by four times, the electric field will decrease about 1 dB, indicating that the disturbed electric field decrease 20 % compared with the original electric field and vice versa. It can be concluded that the variation of electron density before earthquakes may be one important factor influence the variation of SNR.

Shufan Zhao et al.

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Shufan Zhao et al.

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Latest update: 10 Jul 2020
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Short summary
We use satellite data to analyze the precursory anomalies of M7.1 Yushu earthquake occurred in western China through analyzing signal to noise ratio (SNR), and we use full wave model to illustrate a possible mechanism how the anomalies occurred. The results show SNR of VLF radio waves in the ionosphere decreased before Yushu earthquake. The full-wave simulation results confirm the electron density variation in the lower ionosphere will affect the SNR of VLF radio signals.
We use satellite data to analyze the precursory anomalies of M7.1 Yushu earthquake occurred in...
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