Whole mantle shear velocity model SAW24B16

The model SAW24B16 is a VSH model parametrized laterally in spherical harmonics
up to degree 24 (Edmonds normalization) and radially in 16 unevenly spaced splines.

The model was derived with handpicked transverse component waveforms, including:
1. SH body waves (S, SS, S3, S4, ScS, ScS2, ScS3, Sdiff and corresponding depth phases: sS, etc...),
down to a corner frequency of 32 sec
2. 1st & 2nd orbit Love waves
3. 1st & 2nd orbit higher modes
down to a corner frequency of 70 sec

The theoretical framework is a normal mode asymptotic formalism, including both along branch and across branch coupling,
which provides broadband kernels for body waveforms and surface waves (NACT).
Ray theory assumes that the sensitivity to structure of body waves is limited to the infinitesimal ray path and uniform along the ray.
On the other hand, standard surface wave theory ("path average" approximation) assumes that the sensitivity kernel is 1D,
that is, depends only on the average structure between the source and the receiver. The NACT approach takes into account
the finite width of the sensitivity kernel of a body wave (or higher mode surface waves) around the infinitesimal ray, and the variation
of the sensitivity along the ray.

This framework allows the inversion of complete seismogram waveforms, with accurate 2D sensitivity kernels.
The theory used to develop the model is described in :

Xiang-Dong Li and Barbara Romanowicz , "Comparison of global waveform inversions with and without considering
cross-branch modal coupling", Geophys. J. Int. (1995) 121, 695-709. (view Abstract)

The SAW24B16 model is described in :

Charles Mégnin and Barbara Romanowicz , "The shear velocity structure of the mantle from the inversion of of body,
surface and higher modes waveforms", Geophys. J. Int, 143,709-728, 2000. Download a preprint.(1.2 Mb)


Lateral sections of SAW24B16 in the whole mantle.
Cross sections across Africa .
East Pacific cross-sections.
Cross sections across the American continent.
West Pacific cross-sections.
3D map of the -1% isocontour in the whole mantle.
3D map of the -1.25% isocontour across 670 km in the whole mantle.
3D map of the West Pacific subduction across 670 km.
Spectral decomposition of SAW24B16.


Download SAW24B16 (expanded on a 2x2 degree grid) (2.3 Mb)

Alternatively, download SAW24B16 coefficients, the code to read them, (65 Mb)
and the readme file.

For all enquiries, please contact Barbara Romanowicz:

Last update : 2/15/2003