- Gravity investigations do have certain known limitations, the two most prominent perhaps being deep resolution and the non-uniqueness of the solution. We utilized the principle of the physical geometry a two-dimensional dike in the inversion process across tectonic line in the Chubu District, Honshu—in the Japan Alps. The location is probably where the Tsunan-Matsumoto tectonic line interacts with the Itoigawa-Shizuoka Tectonic Line (ISTL). Two-dimensional modeling results consistent with previous works on gravity and reflection and/or refraction prospecting are given to depict the probable sub-surface structure. We conclude that the Bouguer gravity anomaly low to the Southwest or Western side of the tectonic trace is due to thrust of lower density sedimentary rocks deeper into the higher density lower crust to a depth range of approximately 3.5∼4.0 km below the Earth surface.