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The 1D model

The 1D starting model is SEMum2.3, in a PREM-like format. Download this file for the background model.

The file contains the 1D model and the 3D global variations:

 ls SEMum2.3_S6X4_Final_ZeroMean*

This file also contains the crustal correction files (in level 6 spherical splines) needed for the NACT inversion and the Crust and Moho ascii files needed for the RegSEM simulation.

 ls crust_corrections/
 corr_msc_S_fund.grid_6.A3d         corr_msc_T_fund.grid_6.A3d  
 corr_msc_S_over1-over5.grid_6.A3d  corr_msc_T_over1-over5.grid_6.A3d
 ls RegSEM/
 Crust.asc.SEMum2_Final  Moho.asc.SEMum2_Final

The 3D model

The dlnVs and dlnX files are in Ascii format for depths between 40km to 400km in 10km increment. The file format is long lat dlnVs (or dln X). Please apply the 1D reference model (S/background.vs.txt and X/background_x.txt) to get the absolute values.

The model is downloaded here S model and X model.


1) for the continent region it follows a Crust 2.0-like Moho tomography, so the velocity comparison better starts at 50 km; in the oceans the Moho was fixed at 30km (see Scott's and Ved's papers for the detail).

2) the model given there is a global model, but only the North American region was inverted and the rest of the world was fixed (as in Scott's SEMum2). You can probably follow the map here to find its spatial limit.

3) since no body-wave waveforms were used in the inversion, the depth sensitivity is weak getting down to the transition zone depth.

The Crust Model

The crust used for the RegSEM simulation can be downloaded here: File:Crust.Moho.asci.tar.gz.

The file contains two ascii files needed by RegSEM

 Crust.asc.SEMum2_Final Crust mode
 Moho.asc.SEMum2_Final Moho depth

Note the Crust model (Crust.asc.SEMum2_Final) is a smooth model, and takes the PREM-like format:


 -90.0000     0.0000 5    #lat lon number_of_depth_nodes
 0.00000    2.61888    5.50456    3.25332   99900.00     300.00    5.50456    3.26572    1.00000   
 6.26527    2.59548    5.37242    3.18016   99900.00     300.00    5.37242    3.19228    1.00000  
 18.14200    2.64491    5.64493    3.32975   99900.00     300.00    5.64493    3.34244    1.00000  
 30.01873    3.04744    7.26644    4.16199   99900.00     300.00    7.26644    4.17786    1.00000  
 36.28400    3.20961    7.76620    4.41981   99900.00     300.00    7.76620    4.43666    1.00000


and for depths between the nodes the values need to be interpolated. Also the Moho depth saturates at 30km depths.

The smooth crust model is calibrated to mimic the seismic response of the earth's crust, as seen through observations of surface-wave group-velocity dispersion, by introducing crustal radial anisotropy (Backus, 1962 and Capdeville and Marigo, 2007). See the technique proposed in Lekić and Romanowicz (2011) and later refined by French et al. (2013)).

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