Magnetotelluric monitoring of the seismically active Kamchatka region

The results of observations of the low-frequency magnetotelluric field in t he Shipunskii Promontory seismic source zone during 1993 are discussed. The geoelectrical inhomogeneity of the medium is studied at periods from 200 t o 2500 s. The distortion pattern of magnetotelluric sounding curves is stud ied. It is shown that, along all directions, they are not free from the inf luence of near-surface local geoelectrical inhomogeneities. Time series of the modulus and phase of the impedance Z(xy) are examined at a period of 25 00 s. Anomalous variations attaining 150-170% are revealed in the behavior of the modulus. They coincide in time with enhanced seismicity periods, whe n strong earthquakes occurred. The impedance anomalies are caused by galvan ic effects that can be regarded as seismogalvanic effects relevant to the p roblem of earthquake prediction.