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fault attributes

diagram of fault attributesFaults can move horizontally to the left or right and/or vertically, and the rake of a fault results from a combination of vertical (dip) and horizontal vectors. Rake = angular slip direction of hanging wall block measured in the fault plane and from the dip vector.

Net-slip comprises dip vector component and horizontal vector components.
a. net-slip = total slip of fault.
b. dip-slip = dip-parallel slip component.
c. strike-slip = strike-parallel slip component.
d. vertical-throw = vertical component of net-slip.
e. horizontal-throw = horizontal component of net-slip.
f. heave = stratigraphic heave = apparent horizontal component of the net-slip.

diagram comparing vertical vs stratigraphic throw

Vertical throw, which is the vertical component of net-slip, is different for dipping strata than stratigraphic throw, which is the vertical offset of faulted strata.

If the hanging wall, which lies above the fault, moves downward relative to the footwall, then the fault (as in diagram) is a normal fault. A detachment fault is a regional, low-angle, listric normal fault formed during crustal extension. Listric faults are curved normal faults in which the fault surface in concave upwards because the main detachment fracture following a curved path rather than a planar path. Slumps are listric faults.

diagram of paired horst and graben faultsCrustal extension stresses create sunken graben blocks bounded by parallel normal faults and lying between horst blocks that lie higher than the sunken graben blocks. Compressional forces during orogenies can elevate horst blocks.

If the hanging wall is thrust upward above the footwall, then the fault is a reverse fault. A thrust fault is the special case of low dip-angle faults that formed during regional compressional deformation.

If the predominant movement is in the horizontal direction, then the fault is a strike-slip fault (transform fault or wrench fault). The term tear fault can be used to indicate a steeply-dipping wrench fault that bounds or cuts the hanging wall of a thrust or normal fault (also used for mode III faults).

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