faultsfaulting

7/30/2019 FaultsFaulting

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Faults and Faulting

Earth Structure (2nd

Edition), 2004W.W. Norton & Co, New York

Slide show by Ben van der Pluijm

WW Norton; unless noted otherwise


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EarthStructure (2nd ed) 29/14/2010

Faults


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Faults, fault zones and shear zones


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Fault Types


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Fault Types

DePaor, 2002


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Offset terminology


7/30 EarthStructure (2nd ed) 79/14/2010

Extensional and contractional fault regimes

(a) Starting condition, (b) extension, and

(c) contraction. Note the respective horizontal

length changes.



Alpine Thrusts



Thrust: Ramps and Flats

Ramp anticline

(a) Cross section showing

the geometry of ramps and

flats along a thrust fault. The

fault geometry is shown prior

to displacement on the fault.

(b) Cross section illustrating

hanging-wall and footwallflats and ramps. Segment AB

is a hanging-wall flat on a

footwall flat. Segment BC is

a hanging-wall flat on a

footwall ramp. Segment CD

is a hangingwall ramp on a

footwall flat, and segmentDE is a hanging-wall flat on a

footwall flat.



Klippe and Window

Block diagram illustrating klippe, window (or

fenster), allochthon (gray), and autochthon(stippled) in a thrust-faulted region. Note that

the minimum fault displacement is defined by

the farthest distance between thrust outcrops

in klippe and window.



Normal Fault



Low-angle normal fault (detachment)

Whipple Mtns



Strike-slip Fault



Fault bends

Map-view illustrations of

(a) a restraining bend

and (b) a releasing bend

along a right-lateral

strike slip fault.



Fault Scaling and Self-similarity

D is 3% of L



Fault terminations

(a) Cross-sectional sketch showing various types of fault terminations. The fault

terminates at the ground surface at point A; at point B, the fault has been cut by a pluton;

at C and D, one fault cuts another; at E, the fault was eroded at an unconformity. (b)

Termination of a fault by merging with another fault (at point A), or by horsetailing (at point

B) and dying out into a zone of ductile deformation (at point C). (c) A series of ramps

merging at depth with a basal detachment.



Fault systems



Canadian Rockies Foreland

Thrusts


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Thrust belts

(US Sevier Belt)




Subsidiary Faults

Growth of R-, R-, and P-shears.

(a) Schematic diagram illustrating

a layer of clay that deforms when

underlying blocks of wood slide

past one another.

(b) Map view of the top surface

of the clay layer, illustrating theorientation of Riedel (R),

conjugate Riedel (R), and P-

shears. Note that the acute

bisector of the R- and R-shears

is parallel to the remote 1

direction.



Fault Surfaces: Striations and Polish



Fault surfaces: fibers


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Fault rock classification

Also: Foliated vs. Non-foliated


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Fault Rocks: Gouge and Cataclasite


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Mylonites/Shear Zones


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Pseudotachylytes


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Fault habit with depth

ES, 8-26

Change in fault character with depth for a steeply dipping

fault. Note the change in fault zone width and types of

structures with depth.


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Fault-related folding


(a) A small flexure develops during shortening of the layers, and a

pronounced anticline-syncline pair develops. (b) En echelon (or stepped)

gashes form in the fold. (c) A fault breaks through the fold, cutting

through a gentle flexure. (d) Geometry of a fault-propagation fold.


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Fault-related folds

(a) Fault-bend fold on a thrust. (b) Folding in a fault zone. (c) Detachment

fold. (d) Drape fold over faulted basement.

(See folds and folding)


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Fault-related folds

fault-propagation fold

fault-bend fold

faultsfaulting

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