Update pages on refraction vs reflection #221
Description
The current link to "http://www.enviroscan.com/home/seismic-refraction-versus-reflection" is broken, as it would appear that that company was bought out.
The current link, "https://www.rettew.com/services/geophysics/seismic-refraction-vs-reflection/" is no where near as detailed as the previous version.
We should capture some of that material for reference. The wayback machine has an archived version of the original text (no images unfortunately): https://web.archive.org/web/20200204051524/http://www.enviroscan.com/home/seismic-refraction-versus-reflection