Inversion of the attenuation data of free oscillations of the Earth (fundamental and first higher modes)

We are looking for an average whole earth model of dissipation by using measurements of the quality factor Q at the IPC Paris for spheroidal and toroidal modes (fundamental modes between 100 and 600 s, first higher modes between 100 and 300 s). For these modes, resolution is poor below 1200 km deep. Separate inversions of spheroidal and toroidal modes give two similar models with three main ranges of large attenuation 100 and 350 km and below 750 km, small dissipation in the middle zone; the lithosphere is badly determined (with rather large attenuation) and it is doubtful that an average earth model can be built for it because of lateral inhomogeneities. Simultaneous inversion gives a similar model if it is built on the same number of eigenvectors, but smoother than the previous models.