Select default 1D model interpolation setting

[pjmaechling]

Based on config file settings, the current 1D background model is returned to users as layers, without interpolating values between layers. LA Basin model is returned using interpolation between layers.
First, Show evidence of these default values.
Then, ask the science group what the default settings should be for UCVMC.

[meihuisu]

./plot_elevation_profile.py -s 32.7567,-115.576 -b 0 -e -40000 -d vs,vp,density -v -250 -c 1d -o 1d.png
./plot_elevation_cross_section.py -b 32.7567,-115.852 -u 32.7567,-115.3 -h 1000 -v -100 -d vs  -c 1d -a d -s 100 -e -40000 -o 1d_vs.png

./plot_elevation_profile.py -s 32.7567,-115.576 -b 0 -e -40000 -d vs,vp,density -v -250 -c bbp1d -o ppb1d.png

./plot_elevation_cross_section.py -b 32.7567,-115.852 -u 32.7567,-115.3 -h 1000 -v -100 -d vs  -c bbp1d -a d -s 100 -e -40000 -o bbp1d_vs.png

1d_vs.png

bbp1d_vs.png

1d.png

ppb1d.png

After turned off the linear interpolation between levels for ppb1d,

bbp1d_vs_none.png

ppb1d_none.png