To show how to read in velocity boundary conditions from files,
example files are provided.

First, untar the given 'velbc_full.tar.gz'.
(e.g., type 'tar xzvf velbc_full.tar.gz')

Each of the velbc files has the following naming scheme: {root}{age}.{# of cap}.

{root} is 'velbc_full' in this example, but can be defined by 'file_vbcs' in 
the input file. {age} is each million years from 'start_age' defined in the 
input file to 0 M.y. {# of cap} is an integer from 1 to 12, the number of 12 
spherical caps.