A 2-YEAR COMPARISON BETWEEN THE FRENCH AND CANADIAN SUPERCONDUCTING GRAVIMETER DATA

This study is devoted to a preliminary comparison of the gravity records provided by two geographically well-separated superconducting gravimeters over a common two-year observing period. The data sets are processed for the first time following exactly the same numerical steps. After a brief description of the observed gravity and pressure signals, we perform a classical least-squares fit to tides, taking into account a single coefficient for the effect of the local barometric pressure fluctuations and a second-order polynomial approximation for the instrumental drift. The results show a totally different drift behaviour between the two instruments. The time fluctuation of the resulting residual gravity signals is shown, as well as the corresponding power spectral density. In particular, we provide detailed statistics on the spectral content of the residual gravity signals. In a subsequent step, we first high-pass filter the observed gravity and pressure signals and then apply an automatic method to detect and remove obvious spikes. A new least-squares fit then provides new residual gravity signals, the power spectral density of which is reduced in all frequency bands, especially in the subtidal band. We finally provide cross-spectral estimates of these two residual gravity sets indicating a further reduction in the power spectral density level.