Repeated Absolute Gravity Measurements and Seasonal Gravity Changes in the Kamioka Mine, Gifu, Japan

Abstract

Since July 2005, we have repeatedly carried out absolute gravity measurements at Kamioka mine, Gifu, in the deep tunnel about 1 km below the ground surface. A superconducting gravimeter was already installed in the same place. The secular changes of gravity have been investigated using the absolute and the superconducting gravimeters. We have detected gravity changes of several tens of µgals (1µgal = 10^-8 ms^-2). The gravity changes detected by the absolute gravimeter show good agreement with gravity residuals in the superconducting gravimeter data. The gravity changes strongly suggest seasonal ones due to hydrological effects, especially to the snow effect.