We use Rg waves (fundamental Rayleigh wave) to measure shear wave velocity and attenuation in the crust in central Finland. We used seismograms from quarry blasts in USSR recorded during the LITHOSCOPE-SVEKA 89 experiment. We deduced from dispersion curves a shear wave velocity model for the upper crust. From the attenuation of Rg waves as a function of frequency, we found the quality factor Qs in the uppermost crust as a function of depth. The quality factor appears to be low (about 100) in the shallow crust and to increase rapidly at depth (to be about 1000). In order to test this result we calulated complete synthetic seismograms for this velocity-attenuation model. We were able to simulate accurately the arrival times and the relative amplitudes of all the major phases present in the actual seismograms (including Pg and Lg waves). This comparison supports the presence of a very attenuative surface layer with a thickness of about 1 km beneath the Baltic shield while the deep crust presents a very weak attenuation. This relatively thick attenuative superficial layer plays an important part in the overal attenuation observed in shield areas. ¿American Geophysical Union 1991