NA07 is a continental-scale model for upper-mantle structure of North America developed on a tessellated icosahedral grid, and is provided as a set of map files in the xyz format of GMT The maps are located at different, unequally spaced depths within the upper mantle, with the depth (in km) being part of the file name.
This type of tesselated icosahedron was fist used in spherical-Earth modeling by B aumgardner et al. (1985) and Wang and Dahlen (1995), who used a spherical spline parameterization. Linear interpolations between values at grid nodes were independently implemented by Constable et al. (1993) in geomagnetic modeling and by Van der Lee and Nolet (1997) in seismic tomography.
NA07 was generated by an inversion of full-waveform wave trains of S waves, multiple S waves, higher-mode surface waves, and fundamental mode Rayleigh waves, uisng 1.5-dimensional sensitivity kernels. Please read Bedle and Van der Lee (2009) for pertinent details.
Download NA07 (20 Mb)
Bedle, H., and S. van der Lee, S-velocity variations beneath North America, J. Geophys. Res., 114, doi:10.1029/2008JB005949, 2009.
Baumgardner, R.B. and P.O. Frederickson, Icosahedral discretization of the two-sphere. SIAM J. Numer. AnM., 22, 1107-1115, 1985.
Constable, C. G., R. L. Parker and P. B. Stark, Geomag- netic field models incorporating frozen-flux constraints, Geophys. J. Int., 113, 419-433, 1993.
Ma, Z., Masters, G., Laske, G., & Pasyanos, M., A comprehensive dispersion model of surface wave phase and group velocity for the globe. Geophysical Journal International, 199(1), 113-135, 2014.
Van der Lee, S. and G. Nolet, Upper-mantle S-velocity structure of North America, J. Geophys. Res., 102, 22,815-22,838, 1997.
Wang, Z., and F. A. Dahlen, "Spherical-spline parameterization of three-dimensional Earth models", Geophysical Research Letters 22, no. 22: 3099-3102, 1995.