A semi-global reference model for electrical conductivity in the mid-mantle beneath the north Pacific region

[1] One-dimensional electrical conductivity structure in the mid-mantle of the one-fourth of the Earth beneath the north Pacific Ocean was obtained by a semi-global electromagnetic induction study. Electromagnetic response functions estimated from electric field variations measured by submarine cables and geomagnetic field variations obtained by magnetic observatories and long-term observations sites were inverted into radially symmetric conductivity distribution by taking the distribution of land and ocean at the surface into account. As a most preferred model, a smooth conductivity-depth profile was obtained with two abrupt increases that possibly correspond to the seismic discontinuities at 410 and 660 km.