- Interpretations of gravity data suffer from the well-known non-uniqueness of the inversion process and consequently, it demands additional apriori information. The prior knowledge of geology and/or geometry besides appearance of the profiles and contours can make the modeling more tractable. Making use of a subset of parameters consisting of the strike, length, attitude and depth extent of the fault we perform gravity inversion analysis across the Itoigawa-Shizuoka Tectonic Line (ISTL) in the Central Ranges-Japan. As a result, a two dimensional model based on gravity data and consistent with previous works on reflection and/or refraction prospecting is given to depict probable sub-surface structure across ISTL. Seismic experiments suggest a thick sedimentary basin to the Southwest or West of tectonic trace. Similar results are corroborated by our analysis where the sedimentary rocks to the Southwest or West are at depths of 3-3.5 km and the structure narrows westwards.