Abstract:
This study investigates variations of the vertical component of the electrotelluric field (ETF) before and after earthquakes that occurred during 2024-2025. Data from two stations located in the south of Sakhalin Island in the central («Yuzhno-Sakhalinsk») and western («Kolhoznoe») parts were analyzed. Buried metal plates with an area of $0.25\ m^2$ were used as field strength sensors. At the «Kolhoznoe» station, cylindrical lead electrodes were also employed for measurements. Recording of the vertical ETF in the frequency range up to 10 Hz was conducted in quasi-real-time mode from January 2024 to the present. The aim of the study is to test the hypothesis regarding the possible use of variations of the vertical component of the ETF as earthquake precursors. The specific task of this work is to investigate variations of the vertical component of the ETF at two stations in the southern part of Sakhalin Island and to analyze the relationship with local seismicity. Based on the ETF measurements, periods with high levels of vertical field strength, not associated with seasonality, have been identified. Seismic events with magnitudes $M\geq 2$, recorded in the south of Sakhalin, occur predominantly during these periods. The obtained results may indicate that variations in the vertical ETF reflect local changes in the seismic regime.
Keywords:electrotelluric field, vertical component, data recording, changes in geophysical fields, seismic events, earthquake precursor.
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