A modification of the moment tensor inversion method is presented, which significantly improves depth and source mechanism resolution from complex spectra of Rayleigh waves in the period range 30--90 s. The procedure consists of two steps: First, the spectra are separated at each frequency into a depth sensitive and a depth insensitive component. The latter consists of biases and errors and is discarded. The former is then used alone to invert for depth and source mechanism. Each of the five resolvable components of the moment tensor can be monitored separately as a function of depth. The latter is best determined from the residuals curves corresponding to the dominant components, which depend on the source mechanism. Several examples of application are given. It appears that phase velocities determined using one larger event with a well constrained mechanism and depth from body waves can be successfully used as path corrections in a source region around it, 500--1000 km in radius. For other events in the region, depth can now be constrained to within ¿5 km and source mechanism, to within ¿5¿ in each of the three angles: strike, dip and slip. On the other hand, if only a rough estimate of depth and source mechanism is needed, regionalized phase velocities can now be used for path corrections. Finally, it is shown that, for certain depth ranges and certain mechanisms, the choice of the periods used in the inversions can be crucial in avoiding biases in depth determination.