Study of Long-term Gravity Variations, Based on Data of the GGP Co-operation

Abstract

Abstract The study continues a paper with the same title, presented at the Earth Tides Symposium 2000 in Mizusawa. Now data series from 12 GGP stations could be included (BE, BO, CA, CB, MB, MC, MO, PO, ST, SU, VI, WE). The length of the data series varies between 4 and 18 years. From some stations hydrological data were available. In most cases, the drift of the gravimeters was low and nearly linear. No absolute gravity measurements were available to support the estimation of the instrumental drift. Again the annual wave and the Chandler wobble were separated by fitting two sinusoidal functions with periods of 365.25 and 432 days to the residual gravity. As to be expected, the results for the individual stations move closer together and become more reliable. The δ-values of the Chandler wobble approach to 1.16. The correspondent values of the annual wobble are slightly smaller but demonstrate considerable variability. The phase lags of both phenomena are in the order of a few degrees.