A SIMPLE METHOD TO RETRIEVE THE COMPLEX EIGENFREQUENCY OF THE EARTHS NEARLY DIURNAL-FREE WOBBLE - APPLICATION TO THE STRASBOURG SUPERCONDUCTING GRAVIMETER DATA

We have analysed more than four years of data from the Strasbourg supe rconducting gravimeter to retrieve the period and damping of the nearl y diurnal-free wobble (NDFW). The removal of noise spikes is found to be crucial for an accurate determination of tidal-wave amplitudes and phases. A new simple algorithm is derived which allows an analytical s olution for the NDFW period and damping using the complex gravimetric factors of three resonant diurnal waves. The results show a huge reduc tion of the confidence intervals when compared with a previous investi gation from a Lacoste Romberg spring meter operated at the same statio n. Our results are in close agreement with values obtained from two ot her European superconducting gravimeters. The results are also compare d with respect to values inferred from very long baseline interferomet ry (VLBI) measurements.