PERFORMANCE OF WIELANDT-STRECKEISEN STS-1 SEISMOMETERS IN THE TIDAL DOMAIN - PRELIMINARY-RESULTS

The aim of this work is to show that STS-1 seismometers are able to provide a signal with a very long period vertical component which can be used for Earth tide studies provided a number of recording conditions are improved. We use data from the GEOSCOPE network for BNG (Bangui, Central African Republic), MBO (M'bour, Senegal), CRZF (Crozet, TAAF (Terres Australes et Antarctiques Francaises), Indian Ocean), ECH (Echery, France) and PAF (Port-aux-Francais, Kerguelen, TAAF, Indian Ocean) stations operated by the Ecole et Observatoire de Physique du Globe de Strasbourg (EOPGS) and Institut Francais de Recherche Scientifique pour le Developpement en Cooperation (ORSTOM). These data are analysed with a least-squares adjustment method to fit the Earth tidal waves, and the results for these stations are compared. Special attention is paid to the comparison of results from ECH with those from the superconducting gravimeter of Strasbourg (J-9). For several stations used in this study (CRZF, MBO and ECH) the results are promising, but they are disappointing for others (PAF and BNG). We did not find any clear reason for such a difference in quality. We propose some improvements that will enable researchers to achieve a better recording of this long-period signal and obtain higher-quality data allowing gravimetric studies from global seismological networks.