Magnetotelluric monitoring of the seismically active Kamchatka region

The results of observations of the low-frequency magnetotelluric field in the Shipunskii Promontory seismic source zone during 1993 are discussed. The geoelectrical inhomogeneity of the medium is studied at periods from 200 to 2500 s. The distortion pattern of magnetotelluric sounding curves is studied. It is shown that, along all directions, they are not free from the influence of near-surface local geoelectrical inhomogeneities. Time series of the modulus and phase of the impedance Z(xy) are examined at a period of 2500 s. Anomalous variations attaining 150-170% are revealed in the behavior of the modulus. They coincide in time with enhanced seismicity periods, when strong earthquakes occurred. The impedance anomalies are caused by galvanic effects that can be regarded as seismogalvanic effects relevant to the problem of earthquake prediction.