Quality Control - 3-D Structural Geology - page 292

Fig. 10.17. Use of the expansion index to test unit correlations. An expansion index of less than one
implies reverse fault movement or a miscorrelation across a normal fault
Fig. 10.18. Presence of a fault interpreted from anomalies in the expansion index and vertical separa-
tion. a A misinterpretation of the hangingwall of fault f 1 that gives an expansion index of less than one
for unit 2 and a fault throw that decreases and then increases with depth. b The anomalous thinness of
unit 2 in well B is explained by normal fault f 2 . C is a well that would penetrate an unfaulted section in
the hangingwall of the fault f 1
preted growth stratigraphy (Fig. 10.18a) shows the separation to decrease downward
and then to increase again. The correct interpretation (Fig. 10.18b) shows a continuing
increase of vertical separation downward.