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6-6. NETWORK-MT Project
NETWORK-MT is one of the major components of the Earthquake Prediction
Program. This experiment aims to reveal the mean nation-wide distribution
of electrical conductivity in the Earth. Major experimental efforts focus
on measuring electric field variations over 10-30 km distances using commercial
telephone lines. Scientists from eleven universities and institutions in
Japan are collaborating in this project.
Fig.1. Cumulative plots of the sites in which NETWORK-
MT observations were made since 1994 under the Earthquake Prediction Research
program (in red circles). Green circles indicate the sites of continuous
monitoring of the telluric voltage differences. Measurements in other areas
were taken in 1989-1993 in other projects.
Fig.2. Spatial distribution of phase of Network-MT impedances in NE-Japan
(period: 64 minutes). Impedances, whose electric and magnetic field directions
are respectively EW and NS, are shown here. Larger phase value indicates
the existence of lower resistivity bodies in the deeper portion. Such high
phase values are detected in the backarc side of Tohoku district along
the strike of the Tohoku arc.
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