Numerical 3D modeling of the magnetotelluric field in Kamchatka
We consider the key features in the responses of magnetic tippers and MTS curves to the sharp contrast in electric conductivity at the interface between the land and the sea waters of the Sea of Okhotsk and the Pacific bounding Kamchatka. The zones with different intensity of the coast effect are revealed. Stronger manifestations of the effect are found to occur in the East Kamchatka, which is related to the induction effects of the electric currents concentrated in the Kuril-Kamchatka trench. Indentation of the coastline resulted in the appearance of three-dimensional (3D) effects in the magnetotelluric field of the eastern Kamchatka. These effects in the variations of the geomagnetic field are vanishing with an increasing period, giving room to low-frequency effects in the MT field, which are associated with the flow of electric currents around Kamchatka (the around-flow effect). It is shown that the transverse MTS curves over the entire region of Kamchatka suffer from the S effect at low frequencies and do not characterize the deep geoelectric structure. Only in the middle segments of the West and Central Kamchatka, the longitudinal MTS curves are weakly subjected to the induction effects and thus reflect the distribution of the deep electric conductivity. On the eastern coast of Kamchatka both the longitudinal and transverse MTS curves are strongly distorted by the 3D effects caused by the abundant capes and bays. The interpretation of MTS data in this region should necessarily invoke the 3D modeling of an MT field.