GMT/Netcdf grid expansions of the SMEAN2 composite tomography
"model". The approach follows that used by Becker and Boschi (G-Cubed,
2002), but uses updated models:

Gypsum-S (Simmons et al., 2011), S40RTS (Ritsema et al., 2011), and
SAVANI (Auer et al., 2014).

All files can be converted to ASCII files with lon-lat-value by GMT

grd2xyz dvs.1.grd > data.lonlatv

for example. 

These grid files were extracted from the original, spherical harmonics
version, which is also included as file d.31.model.ab, and can be used
via the "shansyn" tools, for example, available at

http://www-udc.ig.utexas.edu/external/becker/sdata.html

with the bash script "convert" that is part of this tar file. Shansyn
comes also pre-installed as part of the Unified Geodynamics Earth
Science Computing Environment at

http://www-udc.ig.utexas.edu/external/becker/ugesce.html

The grid file values are given are percentage v_S wave speed variation
related to PREM, with layer averages removed.

The original model was expanded on 58 levels, bottom up, at the depths
indicated in km in the file depths.dat. Note that crustal levels
shallower than 75 km are meaningless.

For any questions or comments, please contact Thorsten Becker at
twb@ig.utexas.edu.

Thorsten Becker, Austin, June 2016