What are the 4 basic classes of faults?

Earthquake Faults

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Dip-Slip Faults

Normal Fault

In a normal fault, the block above the 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] EX., Sierra Nevada/Owens Valley; Basin & Range faults

Quicktime (788 kB)

Reverse Faults

In a reverse fault, the block above the 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: thrust fault, reverse-slip fault or compressional fault] EX., Rocky Mountains, Himalayas

Quicktime (947 kB)

Strike-Slip Fault

In a strike-slip fault, the movement of blocks along a fault is horizontal. 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. If the block on the far side moves to the right, the fault is called right-lateral. The fault motion of a strike-slip fault is caused by shearing forces. Examples: San Andreas Fault, California; Anatolian Fault, Turkey [Other names: transcurrent fault, lateral fault, tear fault or wrench fault.]

Quicktime (935 kB)

Transform Fault

A transform fault is a type of strike-slip fault wherein the relative horizontal slip is accommodating the movement between two ocean ridges or other tectonic boundaries. Additional animations on seafloor spreading and transform faults are available from Tanya Atwater.

Quicktime (4.25 MB)

Oblique Fault

Oblique-slip faulting suggests both dip-slip faulting and strike-slip faulting. It is caused by a combination of shearing and tension or compressional forces. Nearly all faults will have some component of both dip-slip (normal or reverse) and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant.

Quicktime (753 kB)

Fault Models Lecture

Dr. Robert Butler, University of Portland, discusses Faults and Folds

Quicktime (13 MB)

Animations and videos are made in partnership with Earthscope, USGS, and Volcano Video & Graphics.

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