Permalink : http://hdl.handle.net/2115/88555

JaLCDOI : 10.14943/gbhu.86.13

Continuous gravity observation with iGrav superconducting gravimeter (#17) was carried out at the Teshikaga, eastern Hokkaido, from November 2018 to August 2022. Gravity timeseries with correction of tides, atmospheric pressure change, and polar motion indicated characteristic seasonal gravity changes from winter to spring in each year. Rate of gravity increases in the early spring in 2021 and 2022 were smaller than those in 2019 and 2020. The G-WATER[1D] software (Kazama et al., 2012) was applied to estimate the gravity change associated with underground water mass variation due to precipitation, snow cover and melting. Calculated gravity changes using parameters supposed by Yamaga and Nawa (2020) could not explain the above differences. Optimal parameters associated with infiltration process of snowmelt water and the saturated hydraulic conductivity of the soil were searched by try and error. As a result, gradual snowmelt infiltration process with an approximately one-order larger hydraulic conductivity could well explain the 4-time seasonal gravity change observed in winter to early spring.