Experience of the multi-parameters electromagnetic monitoring in the area of Bishkek (Kyrgyzstan)

Development of the multi-parameters electromagnetic (EM) monitoring technology in frequency range 0.1 Hz - 1 MHz is carried out in the area of Bishkek (Kyrgyzstan). The technology includes registration of such EM earthquake precursors, as apparent resistivity variations, ULF magnetic and electrotelluric anomalies, electromagnetic emission and ionosphere disturbances. Two types of equipment are used for the EM monitoring: the audiomagnetotelluric system ACF-4M (0.1-1000 Hz) and the radiomagnetotelluric system RMT-F (1-1000 kHz). The equipment ensure time series registration of electric and magnetic field components, robust data processing, spectral parameters calculations, apparent resistivity and impedance phase determination. The integrated multi-parameters monitoring of the considered precursors is carried out simultaneously and obtaining of informative parameters is differed by methods of measured time series data processing only. For the apparent resistivity variations monitoring we apply the audiomagnetotelluric sounding method in frequency range 7-300 Hz with the sufficiently large investigation depth for decreasing of seasonal and daily factors influence, temperature changes and other weather conditions. In this frequency range natural EM fields are quite stable for reliable data obtaining in any time of day and season with accuracy 0.3 % for apparent resistivity. For ULF magnetic, electrotelluric and electromagnetic emission anomalies study we use the wide-band registration of time-series of electric and magnetic fields in frequency range from 0.1 Hz up to 1 MHz. Ionosphere disturbances are studied in radio (observations of remote radio transmitter's signals) and audio (Schumann resonances observations) frequency ranges. EM emission anomaly was registered before the earthquake of M=3.3 on 4 April 2013 in the monitoring station at 100 km distance to the West from the earthquake epicenter (Issyk-Kul lake area). In the dynamic spectrum of magnetic field horizontal component the anomaly is seen in intervals 10-25 and 70-100 kHz (Fig. 1). The duration of the anomaly is approximately 2 hours before the earthquake. This work was supported by the RFBR (project 13-05-12091). Fig. 1. An example of anomaly in the dynamic spectrum of magnetic field in radio frequency range 10-100 kHz before the earthquake of M=3.3 on 4 April 2013 in the area of Bishkek