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Comparison of the performances of different spring and superconducting gravimeters and STS-2 seismometer at the Gravimetric Observatory of Strasbourg, France

 

Rosat S. 1, Calvo M. 1,2, Hinderer J.1, Riccardi U3, Arnoso J.4, Zürn W.5

 

1 Institut de Physique du Globe de Strasbourg, UMR 7516, Université de Strasbourg/EOST, CNRS, 5 rue Descartes, 67084 Strasbourg Cedex, France (Severine.Rosat@unistra.fr)

2 Observatorio Geofísico Central, Instituto Geográfico Nacional (IGN), Madrid, Spain

3 Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse (DiSTAR), Università Federico II di Napoli, Naples, Italy

4 Instituto de Geociencias (CSIC, UCM), Madrid, Spain

5 Black Forest Observatory of Karlsruhe Institute of Technology and University of Stuttgart, Heubach 206, D-77709 Wolfach, Germany

Studia Geophysica et Geodetica, Volume 59, Pagine online, 2015

Doi: 10.1007/s11200-014-0830-5

Abstract

Stud.Geophys.Geodet 2015 Rosat RiccardiXVetrina DiSTARSince 1973, the Gravimetric Observatory of Strasbourg (France) is located in an old fort named J9 and has been the place for various gravity experiments. We present a comparison of the noise levels of various instruments that are or were continuously recording at J9, including the LaCoste&Romberg Earth-Tide Meter ET-5 (19731985), the GWR Superconducting Gravimeter TT-T005 (19871996), the Superconducting Gravimeter C026 (since 1996), the STS-2 seismometer (since 2010) and the LaCoste&Romberg ET-11 (continuously since October 2010). Besides these instruments, the J9 Observatory has hosted temporary gravity experiments with the Micro-g LaCoste Inc. gPhone-054 May-December 2008 and May-September 2009) and the Micro-g LaCoste Inc. Graviton-EG1194(June-October 2011). We include also in the comparison the absolute gravimeter Micro-g FG5 #206 which is regularly performing absolute gravity measurements at J9 since 1997 and a spring gravimeter Scintrex CG5 which recorded at J9 between March 2009 and February 2010. We present the performances of these various instruments in terms of noise levels using a standardized procedure based on the computation of the residual power spectral densities over a quiet time period. The different responses to atmospheric pressure changes of all the instruments are also investigated. A final part is devoted to the instrumental self-noise of the SG C026, STS-2 and L&R ET-11 using the three channel correlation analysis method applied to 1-Hz data.

 

Key-words: superconducting gravimeter; spring gravimeter; broad-band seismometer; power spectral density; noise level; barometric admittance; three-channel correlation

 

Legenda: Three-channel correlation analysis of the 1 Hz SG C026, L&R ET-11 and STS-2 data on one day (31 July 2012). a) Power Spectral Densities (PSDs) relative to 1 (m/s2)2/Hz of the data; b) PSDs relative to 1 (m/s2)2/Hz of the extracted self-noise and c) coherence (black: SG C026 vs. L&R ET-11; green: SG C026 vs. STS-2; blue: L&R ET-11 vs. STS-2). In thick blue line, we have plotted the STS-2 self-noise model of Wielandt and Widmer-Schnidrig (2002).