PERFORMANCE OF 2 SCINTREX CG3M INSTRUMENTS AT THE 4TH INTERNATIONAL COMPARISON OF ABSOLUTE GRAVIMETERS

Two Scintrex CG3M gravimeters were calibrated and compared with other relative meters (LaCoste-Romberg and Scintrex meters) at the fourth In ternational Comparison of Absolute Gravimeters at Sevres, France (30 M ay to 2 June 1994). LaCoste-Romberg meters were used as reference. Thr ee main experiments were carried out at the Bureau International des P oids et Mesures. First, a calibration of the two Scintrex CG3M meters on a new baseline of five points, spanning a range of about 8 mGal. It is shown that both Scintrex meters provide results similar to within 0,005 mGal, even in noisy places, and that Scintrex results are simila r to those of LaCoste-Romber,o instruments to within an accuracy bette r than 0,010 mGal. Second, measurements of vertical gradient at four p oints were carried out. The results for the Scintrex meters lie within 0,007 mGal/m and are similar to those of LaCoste-Romberg meters to wi thin an accuracy of around 0,010 mGal/m. Third, a series of continuous records (each of about 10 minutes) was carried out with three LaCoste -Romberg and the Scintrex meters at four adjacent points. A repeatabil ity of better than 0,005 mGal was obtained for one Scintrex meter. The re is a difference of 0,010 mGal with LaCoste-Romberg data, These resu lts confirm that the Scintrex meter is suitable for measuring small gr avity differences, similar to those observed on active volcanoes.