Tides, earthquakes and ground noise as seen by the absolute gravimeter FG5 and its superspring; comparison with a superconducting gravimeter and a broadband seismometer

Results are presented of a comparison between different instruments (an absolute gravimeter FG5, a superconducting gravimeter C026 and a broadband seismometer STS-2) which have been operated in parallel at the same site in Strasbourg (France). Thanks to a fast sampling technique (20 Hz), we first present the position and coil output signals from the superspring of the FG5, which acts as a long-period seismograph, and compare it with the ground-motion signal directly observed with the seismometer STS-2. The effect on the absolute gravimeter (AG) measurements of a large earthquake (Peru, M = 8. 1) in June 2001 is also shown. We finally investigate how well Earth tides are retrieved on both the absolute and the superconducting gravimeters and give a comparison in the spectral domain of their respective noise levels.