[H-TT20] New Developments in Shallow Geophysics

[HTT20-P05] Detection of water mass variation in a slope by simultaneous continuous gravity observations on surface and in a tunnel

*Kazunari Nawa¹, Yuichi Imanishi², Takeshi Kimura³ (1.National Institute of Advanced Industrial Science and Technology, 2.ERI, Univ. Tokyo, 3.NIED)

Gravity observations are a powerful tool for detecting subsurface mass change. Gravimeters have sufficient sensitivity to detect microGal-level gravity changes due to groundwater level changes and soil water content variations. Recently, several gravimeters have been used to detect land water changes with high accuracy. We have detected temporal gravity variations in daily to monthly timescales corresponding to the water content change in the slope above the horizontal tunnel of F-net Ishigaki station (IGK), using the long-term gravity data of gPhone gravimeter at F-net IGK (underground) and superconducting gravimeter at VERA Ishigakijima station (surface) in Ishigakijima Island, Okinawa, Japan. In order to investigate the gravity and water mass variations over a longer period of time, it is necessary to obtain long-term stable data and to improve the accuracy and calibration of the instrumental drift.