Fault Types: 3 Basic responses to stress

How does rock respond to stress?

A fault is a rock fracture where the two sides have been displaced relative to each other.  Faults are categorized into three general groups based on the sense of slip or movement.

SEE TABS ABOVE for stand-alone versions of each fault type.

This clip includes selected excerpts from the more-in-depth animation, "Earthquake Faults, Plate Boundaries, & Stress

Normal faultthe block above the inclined fault moves down relative to the block below the fault. This fault motion is caused by tensional forces and results in extension. [Other names: normal-slip fault, tensional fault or gravity fault] Examples include Basin & Range faults.

Reverse faultthe block above the inclined fault moves up relative to the block below the fault. This fault motion is caused by compressional forces and results in shortening. A reverse fault is called a thrust fault if the dip of the fault plane is small. [Other names: reverse-slip fault or compressional fault.] Examples include the Rocky Mountains and the Himalayan Mountains.

Strike-slip fault—movement of blocks along a fault is horizontal and the fault plane is nearly vertical. If the block on the far side of the fault moves to the left, as shown in this animation, the fault is called left-lateral (Figure 2). If it moves to the right, the fault is called right-lateral. The fault motion of a strike-slip fault is caused by shearing forces. [Other names: trans current fault, lateral fault, tear fault or wrench fault.]  Examples include the San Andreas Fault, California; Anatolian Fault, Turkey.

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