Gravity measurements have been conducted at 68 stations to focus on west-northwest trending Naguri fault (NGF), which is supposed to be the northern extension of Tachikawa fault. It is found in the Bouguer anomaly map that iso-anomaly contour-lines are distorted due to the NGF left-lateral horizontal displacement, the amount of which is presumed to be a few kilometers. The vertically dipping fault plane cuts the Chichibu formation and presumably the underlying Mikabu-Sambagawa metamorphic rocks at a depth of about 1.2km.
