Geology Reference
In-Depth Information
of the blocks (Fig. 11.25a,b). Otherwise, external rotations can greatly change the amount
of strain inferred from the domino geometry. To show the potential pitfall, an origi-
nal set of domino blocks (Fig. 11.25a) is stretched 18.3% (Eq. 11.37, Fig. 11.25b), then
rotated 15°. A counterclockwise external rotation of the stretched dominoes of 15°
(Fig. 11.23c) produces horizontal bedding and faults having their original dips. Ac-
cording to Eq. 11.37, using a horizontal reference line, the domino strain would be
zero because the bedding and faults are not rotated. From a median surface reference
line, the strain remains 18.3%. A 15° clockwise rotation of the dominoes (Fig. 11.25d)
increases the bedding dip and decreases the fault dip with respect to the horizontal
Fig. 11.25.
Effect of external rotation on strain inferred from domino block geometry
a
Unrotated domi-
noes.
b
Internal rotation of domino blocks, without external rotation, 18.3% extension.
c
15° counter-
clockwise rotation of
b
.
d
15° clockwise rotation of
b
Fig. 11.26.
Domino model applied to example in Basin and Range Province of the western U.S.
a
East-
west cross section from the Wasatch fault to Bear Lake, about 100 km north of Salt Lake City, Utah (after
Westaway 1991).
b
Measurements for domino-model strain calculation
