The files in this tar-package describe the mean p-wave tomography
model "pmean" of Becker and Boschi (G-Cubed, 3, 2001GC000168, 2002) on
a two by two degree grid expansion. The original model is expanded on
spherical harmonics up to degree 31 laterally and in discrete layers
radially (even, 143.55 km spacing). Pmean is based on an average of
recent Harvard and MIT global intermediate wavelength p-wave
tomography models and was constructed as an ad-hoc reference model for
geodynamic interpretations. 

We have found that pmean performs well in velocity inversions as in
Becker and O'Connell (G-Cubed, 2, 2001GC000171, 2001). It's
correspondent s-wave model, smean, also outperforms all other
individual models in geoid inversions as in Steinberger (PEPI, 118,
241, 2001) (B. Steinberger, pers. comm.). See the G-Cubed article for
details about the construction of pmean and references to the original
models.

List of files:

- depths.dat: 
	mid-layer depths in km, from 2799.22 (layer 1) to 71.775
	(layer 20).

- pmean.i.dat: 
	model values at mid-cell location for layers i=1,2,...,20.
	Cells are in row (or "scanline", GMT: -ZTLa) format, i.e. the
	data are given in 2 degree steps starting at the North pole
	(latitude 90N) and longitude 0W, going up to longitude 360W,
	then decreasing the latitude to 88N, and so on until latitude
	-90N. Therefore, each .dat file has 181 * 91 = 16471 entries.
	All model values are in relative wave speed deviations from
	PREM in percent.
- xy.dat:
	The coordinates of the pmean.i.dat entries. Example:

	paste xy.dat pmean.1.dat > pmean.1.xyz

	gives you (under UNIX) the lowermost layer of pmean in
	lon/lat/z-value format.	

- README.pmean:
	this readme file

- pmean.20.ps: 
	plot of the uppermost layer for reference.


Contact me if you have any questions about the model format.

Thorsten Becker, 07/15/02
thwbecker@post.harvard.edu
