Faults:Faults: Are fractures that have appreciable movement parallel to their Are fractures that have appreciable movement parallel to their plane. plane.

Faults may be hundred of meters or a few centimeters in length. Faults may be hundred of meters or a few centimeters in length.

FAULTFAULT

Fault planeFault plane: : Surface that the Surface that the movement has taken place movement has taken place within the fault. On this within the fault. On this surface the dip and strike of surface the dip and strike of the fault is measured.the fault is measured.

Hanging wall: Hanging wall: The rock The rock mass resting on the fault mass resting on the fault plane.plane.

Footwall: Footwall: The rock mass The rock mass beneath the fault plane.beneath the fault plane.

Fault planeFault plane: : Surface that the Surface that the movement has taken place movement has taken place within the fault. On this within the fault. On this surface the dip and strike of surface the dip and strike of the fault is measured.the fault is measured.

Hanging wall: Hanging wall: The rock The rock mass resting on the fault mass resting on the fault plane.plane.

Footwall: Footwall: The rock mass The rock mass beneath the fault plane.beneath the fault plane.

Parts of The FaultsParts of The Faults

Separation:Separation: The amount of The amount of apparent offset of a faulted apparent offset of a faulted surface, measured in specified surface, measured in specified direction. There are strike direction. There are strike separation, dip separation, and separation, dip separation, and net separation. net separation.

Heave:Heave: The horizontal The horizontal component of dip separation component of dip separation measured perpendicular to strike measured perpendicular to strike of the fault.of the fault.

Throw:Throw: The vertical component The vertical component measured in vertical plane measured in vertical plane containing the dip.containing the dip.

Normal FaultsNormal Faults

Thrust FaultThrust FaultThrust Faults: In the thrust

faults the hanging wall has moved up relative to the footwall (dip angle 30º or less)

Reverse Faults: Are similar to the thrust faults regarding the sense of motion but the dip angle of the fault plane is 45º or more

Thrust faults usually Thrust faults usually formed in areas of formed in areas of comperssional regime. comperssional regime.

Thrust FaultsThrust Faults

Strike-Slip FaultStrike-Slip FaultStrike-slip Faults: Are faults

that have movement along strikes.

There are two types of strike slip faults:

A] Right lateral strike-slip fault (dextral): Where the side opposite the observer moves to the right.

B] Left lateral strike-slip fault (sinistral): Where the side opposite the observer moves to the left.

Note that the same sense of Note that the same sense of movement will also be movement will also be observed from the other side observed from the other side of the fault.of the fault.

Strike-Slip Strike-Slip FaultsFaults

Transform FaultsTransform FaultsTransform Faults:Transform Faults: Are a Are a

type of strike-slip faulttype of strike-slip fault (defined by Wilson 1965). (defined by Wilson 1965). They form due to They form due to the the differences in motion differences in motion between lithospheric between lithospheric plates.plates. They are They are basically occur where basically occur where type of plate boundary type of plate boundary is transformed into is transformed into anotheranother..

Main types of transform Main types of transform faults arefaults are::

Ridge-RidgeRidge-Ridge Ridge-ArcRidge-Arc Arc-ArcArc-Arc

Types of Faults•Dip-slip faults have movement

parallel to the dip of the fault plane

–In normal faults, the hanging-wall block has moved down relative to the footwall block

–In reverse faults, the hanging-wall block has moved up relative to the footwall block

Types of Faults•Dip-slip faults have movement

parallel to the dip of the fault plane

–Fault blocks, bounded by normal faults, that drop down or are uplifted are known as grabens

and horsts, respectively

•Grabens associated with divergent plate boundaries are called rifts

–Thrust faults are reverse faults with dip angles less than 30° from horizontal

Different Type of Faults