Laboratory Manual for Introductory Geology 4e

FIGURE 10.7 Hanging wall, footwall, and the classification of faults.
If you look across a strike-slip fault and the
opposite side moved to your right, it’s a
right-lateral fault. If the opposite side
moved to your left, it’s a left-lateral fault.
Weathered normal fault scarp
This fault is
left-lateral.
Half arrows indicate
the sense of slip.
Hanging
wall block
Footwall block
(a) The hanging wall is above the fault surface; the footwall is below.
Fault scarp
Strike-slip faults
tend to be vertical.
Footwall
block
Hangingwall
block
(b) On a strike-slip fault, one block slides
laterally past another, so no vertical displacement
takes place.
(c) Normal faults form during extension
of the crust. The hanging wall moves down.
60° 30°
(d) Reverse faults form during shortening of the
crust. The hanging wall moves up, and the fault
is steep.
(e) Thrust faults also form during shortening.
The fault’s slope is gentle (less than 30°).
EXERCISE 10.7
Faulted Strata on a Block Diagram
Name:
Course:
The following questions refer to the figures on the next page.
Section:
Date:
(a) Block 1 shows a vertical fault cutting across a nonplunging syncline. Complete the block diagram by adding arrows
to show the direction of displacement across the fault and by adding colored bands for the appropriate stratigraphic
units in the blank areas. What type of fault is it?
(b) Block 2 shows a dip-slip fault. Is this a normal or reverse fault?
(continued)
10.3 WORKING WITH BLOCK DIAGRAMS
251