[CIG-SEISMO] Issue with material properties in SW4

[Shahar Shani-Kadmiel]

I am trying to prescribe a custom gradient to material properties as the builtin gradient option in SW4 does not apply to Qp and Qs and also because I am interested in a slightly more complex gradient than a simple linear one. When checking the material properties stored in the images written by SW4 I noticed that the values are off by quite a bit.

I have created a sample input file which produces the issue that can be downloaded here <https://www.dropbox.com/s/eoao8l6wdxtmfyg/material_test.sw4?dl=1>.

I don't really understand where the issue originates. It might be just wrong data in the SW4 image file(I hope that is the case) because SW4 reports the correct values in stdout (full stdout here <https://www.dropbox.com/s/0mycmrfi66tr2p4/stdout.txt?dl=1>):

       ----------- Material properties ranges ---------------
       1.61000000e+03 kg/m^3 <=  Density <= 1.99000000e+03 kg/m^3
       6.50000000e+02 m/s    <=  Vp      <= 9.64000000e+02 m/s
       3.50000000e+02 m/s    <=  Vs      <= 6.66000000e+02 m/s
       1.44736842e+00        <=  Vp/Vs   <= 1.85714286e+00
       1.97225000e+08 Pa     <=  mu      <= 8.82676440e+08 Pa
       5.95263090e+07 Pa     <=  lambda  <= 2.85775000e+08 Pa
       Using attenuation 
       2.00000000e+00        <=  Qs      <= 5.20000000e+01  
       3.00000000e+00        <=  Qp      <= 1.03000000e+02  
       ------------------------------------------------------
Below is a workflow to demonstrate the issue: (viewable as a static notebook here <http://nbviewer.jupyter.org/urls/dl.dropbox.com/s/gakmdsneom6kesu/SW4_MaterialModel_Issue.ipynb>)

First I parse the input file <https://www.dropbox.com/s/eoao8l6wdxtmfyg/material_test.sw4?dl=1> and plot the desired material properties as they are specified in the block commands.
I then read the Vp, Vs, and rho, cross section images created by SW4 and plot the images
I then plot a sample column from the center of each image array to present the resulting material properties.
Finally I compare the desired and resulting properties side by side and report the min, max, values.
I guess I would like to know if this issue is reproducible on other machines and if so if it is a real issue? That is: Does the SW4 computation actually runs with wrong material properties or does it simply report the wrong values in the image files.

Thanks for your help,

Shahar
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