Resistivity structures along lines A-A’ and B-B’, after removal of the low-sensitivity part. Site numbers are indicated above black triangles. Locations of pressure sources (Murase et al. ) and spasmodic bursts (Konstantinou et al. ) are shown respectively as stars and ellipses in the structure along lines A-A’ and B-B’. The solid lines represent the trajectories of boreholes E202 and E203 drilled by MRSO ().