(Phil, 04/10/2014)

The seismic refraction dipping layers is now under construction. Before the section is complete:

(1) Images need to be reworked and added
(2) The final sentence says averaging v2 and v2 (as does GPG). Quantities need clarification.
(3) Grammar/style query: earlier paragraphs in GPG use "updip velocity" and latter use "up-dip velocity." Text is modified to unhyphenated choice for consistency. But in general: hyphen or no hyphen?