Seismogenic Effects in Variation of the ULF/VLF Emission in a Complex Study of the Lithosphere–Ionosphere Coupling Before an M6.1 Earthquake in the Region of Northern Tien Shan
Salikhov N. Shepetov A. Pak G. Nurakynov S. Ryabov V. Zhukov V.
June 2025Multidisciplinary Digital Publishing Institute (MDPI)
Geosciences (Switzerland)
2025#15Issue 6
A complex study was performed of the disturbances in geophysics parameters that were observed during a short-term period of earthquake preparation. On 4 March 2024, an (Formula presented.) earthquake (N 42.93, E 76.966) occurred with the epicenter 12.2 km apart from the complex of geophysical monitoring. Preparation of the earthquake we detected in real time, 8 days prior to the main shock, when a characteristic cove-like decrease appeared in the gamma-ray flux measured 100 m below the surface of the ground, which observation indicated an approaching earthquake with high probability. Besides the gamma-ray flux, anomalies connected with the earthquake preparation were studied in the variation of the Earth’s natural pulsed electromagnetic field (ENPEMF) at very low frequencies (VLF) (Formula presented.) kHz and (Formula presented.) kHz and at ultra-low frequency (ULF) in the range of 0.001–20 Hz, as well as in the shift of Doppler frequency (DFS) of the ionospheric signal. A drop detected in DFS agrees well with the decrease in gamma radiation background. A sequence of disturbance appearance was revealed, first in the variations of ENPEMF in the VLF band and of the subsurface gamma-ray flux, both of which reflect the activation dynamic of tectonic processes in the lithosphere, and next in the variation of DFS. Two types of earthquake-connected effects may be responsible for the transmission of the perturbation from the lithosphere into the ionosphere: the ionizing gamma-ray flux and the ULF/VLF emission, as direct radiation from the nearby earthquake source. In the article, we emphasize the role of medium ionization in the propagation of seismogenic effects as a channel for realizing the lithosphere–ionosphere coupling.
Doppler frequency shift , earthquake precursor , gamma-ray flux in the borehole , ionosphere , ULF/VLF
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Institute of Ionosphere, Almaty, 050020, Kazakhstan
P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, 119991, Russian Federation
Institute of Ionosphere
P. N. Lebedev Physical Institute of the Russian Academy of Sciences
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