
Near and far offset partial stacks: subcubes from full 3-d cubes.
segy format

inline: 1300-1500, every 2
xline: 1500-2000, every 2
time: 1500-2500 ms
total 25351 traces for each subcube.

xline number stored in bytes 21-26.
inline number (multiplied by 1000) stored in bytes 41-44.
