Abstract
To detect seismic disturbances in the lower ionosphere, we have used the signals of very-lowfrequency radio transmitters and natural radio signals—electromagnetic emission of lightning discharges—atmospherics. On earlier results of observation of atmospherics, it was obtained that the earthquake effects are displayed as weight-hourly amplitude increases on the day of event or within 3 days after them. Possible earthquake precursors are also manifested as one-day (within one to several hours) increases in the amplitude of atmospherics on average 5 - 12 days before the event. Analysis shows that seismic effects in the amplitude of atmospherics have been observed in the case of sufficiently strong (magnitude M > 4.5) and not very deep (usually no deeper than 50 km) earthquakes. The effects of the events of the earthquake with magnitude of 8.2 occurring in the Sea of Okhotsk on 24.05.13 not far from the Kamchatka Peninsula at a depth of 609 km considered in this work have shown that even deep earthquakes may have precursors in the form of disturbances in the lower ionosphere.
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
To detect seismic disturbances in the lower ionosphere, we have used the signals of very-low-frequency radio transmitters and natural radio signals—electromagnetic emission of lightning discharges—atmospherics
Summary
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 (though on the phase relations) of electromagnetic waves in the vicinity of the terminator. Unlike radio signals, the atmospherics allow using only amplitude detection methods for ionospheric disturbances, at the same time they allow azimuthal scanning at a single receiving station in a wide sector (in a broad seismic area). Possible precursors of EQ appeared in one-day (within one to several hours) increases in the amplitude of atmospherics mainly 5 - 12 days before the event. The preliminary analysis shows that the seismic effects in the amplitude
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