Comparison of Data Sets Recorded with the Dual Sphere Superconducting Gravimeter CD 034 at the Geodynamic Observatory Moxa

Since April 1999 the dual sphere superconducting gravimeter CD 034 is operating at the Geodynamic Observatory Moxa (Germany). A comparison of the period range between 20 s and 2 days shows a high similarity of the two data sets. As expected the upper sensor produces a slightly noisier signal than the lower one. Up to now the difference signal of the two sensors gives no indication for the small arbitrary steps older instruments are susceptible to. Regarding the long-period range we find, after eliminating the barometric pressure influence, a long-term trend in both data sets that can be traced back to hydrological effects. The difference of the time series yields a small linear drift signal of presently unknown physical origin.