2-D georesistivity structure in the central part of the northeastern Japanarc

Wide-band (0.002 similar to 20,000 Hz) magnetotelluric measurements (MT) ob servations have been conducted along three traverses in the central Tohoku district of the northeastern Japan are at 86 observation sites since 1990 i n order to image the electrical resistivity structure. We used the impedanc e tensors fully corrected for the three-dimensional galvanic distortion eff ects including static shift effects in order to refine previous 2-D models (discussed in Fujinawa et al., 1997). The subsurface 3-D effects are found to be generally small with the result of a slight difference between the pr esent model and the previously reported one. The modeling results indicate that the crust is homogeneous without an enha nced conductivity zone in the lower crust, in general agreement with result s in the northern part of the Tohoku district. The refined resistivity prof iles delineate more clearly two near-surface conductive anomalies located i n the fracture zone between the Dewa Hill and the Central Basin Range, and in the zone between the Kitakami and Abukuma River regions. Conductors in t he crust west of the Sekiryo Mountain Range generally correlate well with m apped faults or pre-Tertiary tectonic lines. Several buried faults are also suggested from the conductivity data. The electrical resistivity distribut ion and known active faults are integrated to better understand the seismo- tectonics and geologic regime associated with the subduction processes in t he Japan are region.