Researching of quasiperiodic variations in the amplitude of VLF electromagnetic signals from lightning discharges passing over strong earthquakes

Vyacheslav Argunov,Mikhail Gotovtsev,N Salikhov,A Vilayev,B Shevtsov

doi:10.1051/e3sconf/201912703005

Vyacheslav Argunov, Mikhail Gotovtsev + Show 3 more

Open Access

https://doi.org/10.1051/e3sconf/201912703005

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Abstract

The specific features of a method for radiosounding the lower ionosphere over earthquake epicenters using LF electromagnetic signals of thunderstorm sources (atmospherics) have been considered. The effects of shallow-focus earthquakes with magnitudes larger than 4.0 and their precursors manifest themselves in amplitude characteristics of atmospherics. It has been assumed that variations in the signal characteristics are related to disturbances in the lower ionosphere. According to the results of azimuthal scanning, cross sectional dimensions of disturbed regions, as a rule, correspond to the dimensions of the first two Fresnel zones for signals at a frequency of 10 kHz. Azimuthal scanning also indicated that the positions of disturbed regions during and before earthquakes could have a certain dynamics and differ from the projection onto the earthquake epicenter. Quasi-periodic variations of signal amplitude of lightning discharges passing over earthquake epicenters are in details considered. It has been obtained that the period of amplitude modulation makes up 2-3 hours, i.e. in the ionosphere D-layer the same values of the periods of wave phenomena are registered as which are observed in a higher F-region of the ionosphere. The results obtained during the work specify that, at least, in the part of events the seismic disturbances in the ionosphere can be caused by AGW, propagating upwards from the epicentral area.

Highlights

The investigation of manifestations of lithospheric processes in the lower ionosphere is usually done using the signals of very-low-frequency (VLF) or low-frequency (LF) radio transmitters [1,2,3,4,5,6]
Amplitude measurements refer to the rougher methods, it should be noted that in a number of papers [4,5], the amplitude measurements are used in the search of ionospheric precursors of strong earthquakes (EQs), but those measurements are based on the interference of electromagnetic waves in the vicinity of the terminator
It was found that exactly one month before earthquake on 11.03.2011 internal gravity waves (IGW) was observed, with high probability associated with seismic activity

Summary

Introduction

The investigation of manifestations of lithospheric processes in the lower ionosphere is usually done using the signals of very-low-frequency (VLF) or low-frequency (LF) radio transmitters [1,2,3,4,5,6]. Supplementing method for detection of seismic disturbances in the ionosphere, the use of natural radioelectromagnetic emission of lightning discharges— atmospherics can be considered. This method gives the possibility to conduct a monitoring scan of a large seismically active region or of several regions directly from one point. In this paper, these features are considered in relation to the receiving point in the city of Yakutsk

Method used to measure and analyse the parameters of atmospherics

Results

Conclusion