Types of Faults
Faults are distinguished on the basis of the movement of the footwall relative to the hanging wall (Figures 15.29a-e). Dip slip faults are those in which vertical displacement primarily occurs.
Figure 15.29a Normal Fault
Courtesy USGS
A normal fault is one in which the hanging
wall falls down relative to the foot wall due to tensional stress 
. The
Teton Mountains 
in North America are a result of normal faulting. A reverse fault is one in which the hanging wall moves
up relative to the foot wall due to compression . A thrust fault is a reverse fault at 45o angle.
Figure 15.29b Thrust Fault
(a reverse fault at 45o angle)
Courtesy USGS
Figure 15.29c Horst and Graben
Courtesy USGS
A horst forms between two normal faults when a block of rock in the middle remains stationary and the blocks on either side subside. A graben forms when a block of rock falls between two faults. Huge, relatively flat
bottomed valleys, like Death Valley in California ,
are created in this
way. The Basin and Range physiographic province of North America is noted for its faulted mountains (horsts) and flat-bottomed valleys (grabens). Large plateau surfaces form in this fashion. The Basin
and Range Province of North America is noted for its faulted mountains
and flat-bottomed valleys.
Figure 15.29d Strike slip / Transform Fault
Strike slip or
transform faults are those that primarily
exhibit horizontal movement
. Such activity can be discerned from
surface features like offset streams. The San Andreas fault
is a well-known
strike slip fault caused by the Pacific Plate sliding past the North
American Plate. (View a segment of the San Andreas fault in Google Earth)
Oblique faults exhibit both horizontal and vertical movement.
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