5 May 2014

Photoshop as a means of reconstructing fault offset

Posted by Callan Bentley

I saw this fault in Texas, north of the laccolith known as Cristo Rey:

fault_smClick to enlarge

I had a hard time making sense of the offset in my head, though, since the layers were of inconsistent thickness. Several people tried to convince me that the offset was “normal” (that is, right side down), but it still didn’t “click” for me in the field. So I took a photo.

Back at home, I cut my photo in half using Photoshop, and then moved the hanging wall relative to the foot wall, and stopped when I found a match.


…Sure enough, my interlocuters were right. The right side (hanging wall) had indeed moved down relative to the left side (foot wall).


Arrows show “reconstruction faulting” in Photoshop, which is the opposite of actual (apparent) offset.

The real faulting may be associated with the Rio Grande Rift, the more localized flavor of Basin & Range extension around those parts.