Electromagnetic Monitoring During the Aftershock Period of the 2003 Chuya Earthquake in Gorny Altai: Measurement Technique and Results

The article discusses the observation methodology, data interpretation, and results of electromagnetic monitoring with a controlled source for one of the seismically active regions of Siberia—Gorny Altai. Monitoring was carried out during the aftershock period in the epicentral zone of the destructive 2003 Chuya earthquake with M = 7.3. For regular observations, a measurement technique has been developed using several modifications of the transient electromagnetic field (TEM) method to determine variations in electrical resistance and the anisotropy coefficient. Long-term series of these two geoelectric parameters of the section are presented, compared with the characteristics of ongoing seismic events. As a result of the analysis, it was shown that variations in electrical resistance and the electrical anisotropy coefficient reflect the development and gradual decay of the aftershock activity of a powerful earthquake. The advantages of the TEM method and the selected technique for monitoring in complex areas are reflected.