関東地方の重力基盤に見える断裂構造  [in Japanese] The graben structure suggested by the gravimetric basement in the Kanto district, central Japan  [in Japanese]

The gravity map of the Kanto district was compiled with the assumed density 2.0 g/cm^3. The gravity map indicates that high Bouguer anomaly areas exist in Kanto mountains, Tanzawa mountains, Izu peninsula, Yamizo-Tsukuba mountains and the end of Boso peninsula, whose areas corresponds to the circumference of the Kanto basin and low Bouguer anomaly area exist in the coastal area of Tokyo Bay and the middle of the Tone River and the Ara River, whose areas correspond to the center of the Kanto basin. The three dimensional gravimetric analysis is carried out with the assumption of two homogeneous layer model and the dcnsity contrast 0.5 g/cm^3, and well data and outcrop of basement rock were selected as the control points. The gravimetric basement map of the Kanto district suggests that the depth of basement execeds 3 km in the center of Kanto Plain and two graben structure run through the basin in NNE-SSW direction and NW-SE direction. The gravity and aeromagnetic data show that the Median Tectonic Line side slips rightward by about 10 km near Noda city (to the east of Matsubushi SK-1 well) and that Matsubushi SK-1 may belong to the Sambagawa Belt rather than the Ryoke Belt.