README contains the description of the files within the folder. Each text file represents a depth point 
and a corresponding viscosity value such that the viscosity is constant between the top depth point and 
the next depth point when the profile is used for lateral averaging. This also implies that the last value of 
the viscosity is not used.
We define asthenospheric viscosity as the second layer in viscosity profiles based on Steinberger and 
Calderwood (2006).

steinberger_visc.txt   : Contains smooth viscosity profile from Steinberger and Calderwood (2006). Created using 
    radial-visc.txt in $ASPECT_SOURCE_DIR/data/material-model/steinberger. 

stein_smooth.txt       : Contains smooth version of the profile steinberger_visc.txt file. The profile goes 
    through the mid-points rather than the points given in the radial-visc.txt, which are the bottom points 
    of each layer.

stein_smooth_phase.txt : Similar to above but contains the depths at phase transitions 410km, 520km, and 660 km
    present in our material. The viscosity is set based on the profile and this file was only created to align
    the depth layers with the phase boundaries to check for any convergence improvements.

steinberger_source.txt : Similar to stein_smooth.txt but contains the surface point so that the profile is shifted
    up by one point. We do this because in our lateral viscosity averaging scheme, we choose the viscosity value at the 
    top of a layer for averaging.

steinberger_source-1.txt :  Same as above except for the second depth point, which is modified from ~214 km to 300 km. This 
    is done so that we are consistent with the definition of asthenosphere in our material model.

becker_viscosity.txt : Depth-dependent viscosity structure based on Becker 2006.

radial-visc-simple-3.txt, radial-visc-simple-2.txt, rad_viscosity-source-data.txt : These are the source files 
   using the radius fraction (rather than depth) to set the viscosity based on Steinberger and Calderwood (2006), and were  
   used to generate the depth-dependent viscosity  profiles.  

