Fig. 1

a b Location of Mizusawa VLBI Observatory, National Astronomical Observatory of Japan. The red rectangle in a is blown up in the more detailed map (b). c Campus map of Mizusawa VLBI Observatory. The SG is housed inside the building “Obs. Building”. “GNSS1” and “GNSS2” are the GNSS observation sites used in this study. Wn, We, Ww and Ws are the ground water observation wells. d Gravity observation building. “SG” stands for the superconducting gravimeter, and “C” is the point where a compressor and a chiller are installed. Absolute gravity measurements were made at the point “AG”