抄録
A three-dimensional density structure in the shallower crust beneath the Hida Mountains, central Japan, is estimated by using gravity data. We employed seismic velocity structure models both as an initial condition and constraints of gravity structure models. We estimated that an extremely low-density body (density is smaller than 2.1 g/cm3) exists at 4-8 km depth (2 to 6 km below the sea level) beneath Mt. Tateyama (3,015 m) and also along the Hida mountains. Estimated horizontal extent of the body is about 14 km in east to west, about 28 km in north to south directions, respectively, and about 4 km in thickness. The volume of the body is about 1,000 km3. Spatial distribution of the extremely low-density body is well consistent with a low velocity region estimated from studies of seismic tomography.
