Comparison of residual gravity (first- and second-order curve fittings) with precipitation. The residual gravity is derived by subtracting a regression curve from the statistically noise-rejected component (or trend component) of the BAYTAP-G (Tamura et al., 1991). The SD is also shown. Note that the negative direction of the residual gravity indicates an increase in gravity. (a) At a depth of 100 m belowground at the MIU, rainfall data are available from the gPhone at an approximately 100-m horizontal distance (Fig. 1(b)). (b) At the surface of the southeastern flank of Mt. Ontake, no significant difference is seen between the first- and second-order curves. Rainfall data are available from the gPhone at a horizontal distance of approximately 9 km (Fig. 1(c), ONT), and snow depth data are available from the gPhone at a horizontal distance of approximately12 km (Fig. 1(c), KID).