Data Services Products: EMC-SAWum_NA2 A high-resolution North American model of upper mantle structure


SAWum_NA2 North American regional shear velocity model is an isotropic and radially and azimuthally anisotropic Vs model for the North American upper mantle. The isotropic and radial anisotropic portion of the model is developed using long period 3-component fundamental and overtone surface waveforms in the frame work of the Non-linear normal Mode Asymptotic Coupling Theory (Li and Romanowicz, 1995;1996). A joint inversion of surface waveforms and SKS station average datasets is used in the azimuthal anisotropy inversion (Montagner et al. 2000; Romanowicz and yuan 2012).


Name SAWum_NA2
Title A high-resolution North American shear velocity model of upper mantle
Type 3-D full-waveform Earth Model
Sub Type A radially and azimuthally anisotropic shear velocity model
Year 2011
Short Description   SAWum_NA2 is a radially and azimuthally anisotropic shear velocity model, parameterized in terms of isotropic S velocity (Voigt average), the radial anisotropic parameter, xi (V sh 2 /V sv 2) and azimuthal anisotropic strength (dlnG) and fast axis directions (ψ). (see Reference Model below) .
Huaiyu Yuan
Berkeley Seismological Laboratory (Now at Macquarie University, North Ryde, Australia )
University of California, Berkeley
Barbara Romanowicz
Berkeley Seismological Laboratory
University of California, Berkeley
Previous Model
Reference Model A modified version of that used in SEMum model (Lekic and Romanowicz 2011): A smooth, modified version of PREM , with the Q structure of QL6 (Durek and Ekstrom, 1996) that fits normal mode frequencies (see Lekic & Romanowicz, 2011 for more information)
Model Download
Please follow the model home page for associated MATLAB files and the LAB MLD depth file: (metadata ), is the netCDF binary for the above model expressed in km/s.
Model Homepage
Depth Coverage Upper Mantle (25 to 600 km)
Areal Coverage North America; see figure here defining the model space.
Data Set Description Long-period 3-component waveforms (fundamental mode and overtones) from ~200 global events recorded on the global network used in Lekic and Romanowicz 2011, and ~600 global events recorded at North American stations.

Depth cross-sections
Depth cross-sections of isotropic Vs variation (dln Vs; a), radial anisotropy ξ (b), and azimuthal anisotropy (G) fast axis direction©. Location of the profile and surface Precambrian provinces (modified from Whitmeyer and Karlstrom, 2007) are shown in the map (d). Thick and thin horizontal dashed lines in (a-c) show the 220-km depth and the 410-km discontinuity. Anisotropy direction is plotted with respect to the current absolute plate motion (APM) direction. Note: a) the high velocity cratonic root is above 200-250 km depth; b) vertical sense of shear (i.e., ξ <1) is present beneath major suture zones, embedded in the overall horizontal Vsh (ξ>1) dominated lithosphere; and 3) the base of the lithosphere is demarcated by a systematic change of anisotropy fast axis direction towards the current APM direction (red; below 180-240 depth in c). Two lithospheric anisotropic domains can be inferred: the shallow one has the suture zone strike parallel direction (red above 100-150 km) which coincidentally is similar to the current APM direction; and another deeper lithospheric domain which is at a high angle to the current APM. Modified from Yuan and Romanowicz 2010; Yuan et al. 2011.

Citations and DOIs

To cite IRIS DMC Data Products effort:

  • Trabant, C., A. R. Hutko, M. Bahavar, R. Karstens, T. Ahern, and R. Aster (2012), Data Products at the IRIS DMC: Stepping Stones for Research and Other Applications, Seismological Research Letters, 83(5), 846–854, http://doi:10.1785/0220120032.

To cite the source of this Earth model:

To reference the use of this Earth model hosted by EMC:

  • IRIS DMC (2014), Data Services Products: SAWum_NA2, a high-resolution North American model of upper mantle structure, http://doi:10.17611/DP/9992645.

To cite IRIS Earth Model Collaboration (EMC) data product or reference use of its repository:


  • Lekić, V., Romanowicz, B., 2011. Inferring upper-mantle structure by full waveform tomography with the spectral element method. Geophys. J. Int. 185, 799-831.
  • Li, X.-D., Romanowicz, B., 1995. Comparison of global waveform inversions with and without considering cross-branch modal coupling. Geophys. J. Int. 121, 695-709.
  • Li, X., Romanowicz, B., 1996. Global mantle shear velocity model developed using nonlinear asymptotic coupling theory. J. Geophys. Res 101, 22245-22273.
  • Montagner, J.-P., Griot-Pommera, D.-A., Lave, J., 2000. How to relate body wave and surface wave anisotropy? J. Geophys. Res. 105, 19,015-019,027.
  • Whitmeyer, S.J., Karlstrom, K.E., 2007. Tectonic model for the Proterozoic growth of North America. Geosphere 3, 220-259.
  • Yuan, H., Romanowicz, B., Fischer, K.M., Abt, D., 2011. 3-D shear wave radially and azimuthally anisotropic velocity model of the North American upper mantle. Geophys. J. Int. 184, 1237-1260.


H. Yuan and B. Romanowicz