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Geological Faults

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Saad Raja
Saad Raja

Faults are fractures with movement parallel to their plane, usually caused by seismic activity. Understanding faults is important for engineering structures. There are three main types of faults - normal, thrust, and strike-slip. Normal faults involve the hanging wall moving down relative to the footwall. Thrust faults involve the hanging wall moving up. Strike-slip faults involve lateral movement along the fault plane. Faults can be identified by features like slickensides, mineral growth, and offset stratigraphy. Fault classification helps understand mountain building and plate tectonics. Careful analysis of faults is necessary for safe construction near fault lines.

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University of Azad Jammu and Kashmir Raja Saad Qamar TOPIC FAULTS
Geological Faults
FAULT CLASSIFICATION ANDFAULT CLASSIFICATION AND TERMINALOGYTERMINALOGY Faults:Faults: Are fractures that have appreciableAre fractures that have appreciable movement parallel to their plane.movement parallel to their plane. They produced usually by seismicThey produced usually by seismic activity.activity. Understanding faults is useful inUnderstanding faults is useful in design for long-term stability ofdesign for long-term stability of dams, bridges, buildings and powerdams, bridges, buildings and power plants. The study of fault helpsplants. The study of fault helps understand mountain building.understand mountain building.
Parts of the FaultParts of the Fault Fault planeFault plane: Surface that the movement hasSurface that the movement has taken place within the fault.On this surfacetaken place within the fault.On this surface the dip and strike of the fault is measured.the dip and strike of the fault is measured.  Hanging wall:Hanging wall: The rock mass resting on theThe rock mass resting on the fault plane.fault plane.  Footwall:Footwall: The rock mass beneath the faultThe rock mass beneath the fault plane.plane.  Slip:Slip: Describes the movement parallel to theDescribes the movement parallel to the fault plane.fault plane.  Dip slip: Describes the up and downDip slip: Describes the up and down movement parallel to the dip direction of themovement parallel to the dip direction of the fault.fault.  Strike slip:Strike slip: Applies where movement isApplies where movement is parallel to strike of the fault plane.parallel to strike of the fault plane.  Oblique slip:Oblique slip: Is a combination of strike slipIs a combination of strike slip and dip slip.and dip slip.  Net slip (true displacement): Is the totalNet slip (true displacement): Is the total amount of motion measured parallel to theamount of motion measured parallel to the direction of motiondirection of motion
 Separation:Separation: The amount ofThe amount of apparent offset of a faultedapparent offset of a faulted surface, measured in specifiedsurface, measured in specified direction. There are strikedirection. There are strike separation, dip separation, andseparation, dip separation, and net separation.net separation.  Heave:Heave: The horizontalThe horizontal component of dip separationcomponent of dip separation measured perpendicular to strikemeasured perpendicular to strike of the fault.of the fault.  Throw:Throw: The vertical componentThe vertical component measured in vertical planemeasured in vertical plane containing the dip.containing the dip.
Features on the fault surfaceFeatures on the fault surface  GroovesGrooves (parallel to the(parallel to the movement direction)movement direction)  Growth of fibrous mineralsGrowth of fibrous minerals (parallel to the movement(parallel to the movement direction)direction)  SlickensidesSlickensides are the polishedare the polished fault surfaces.fault surfaces.  Small steps.Small steps. All are considered a kind ofAll are considered a kind of lineation. They indicate thelineation. They indicate the movement relative trend NW,movement relative trend NW, NE … etc.NE … etc. Small steps may also be used toSmall steps may also be used to determine the movementdetermine the movement direction and direction ofdirection and direction of movement of the opposingmovement of the opposing wall. Slicklines usuallywall. Slicklines usually record only the last momentrecord only the last moment event on the fault.event on the fault.
ANDERSON FAULTS CLASSIFICATIONANDERSON FAULTS CLASSIFICATION Anderson (1942) definedAnderson (1942) defined three types of faults:three types of faults:  Normal FaultsNormal Faults  Thrust FaultsThrust Faults  Wrench FaultsWrench Faults (strike slip)(strike slip)
Different Type of Faults
Normal FaultNormal Fault Normal Fault: The hanging wall has moved down relative to the footwall. Graben:Graben: consists of a block that has dropped downconsists of a block that has dropped down between two subparllel normal faults that dip towardsbetween two subparllel normal faults that dip towards each other.each other. HorstHorst :: consists of two subparallel normal faults that dipconsists of two subparallel normal faults that dip away from each other so that the block between the twoaway from each other so that the block between the two faults remains high.faults remains high. Listric:Listric: are normal faults that frequently exhibit (concave-are normal faults that frequently exhibit (concave- up) geometry so that they exhibit steep dip near surfaceup) geometry so that they exhibit steep dip near surface and flatten with depth.and flatten with depth. Normal faults usually found in areas where extensional stress isNormal faults usually found in areas where extensional stress is presentpresent..
Normal FaultsNormal Faults
Thrust FaultThrust Fault Thrust 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 usuallyThrust faults usually formed in areas offormed in areas of comperssional stress.comperssional stress. Thrust FaultThrust Fault
Thrust FaultsThrust Faults
Strike-Slip FaultStrike-Slip Fault Strike-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 ofNote that the same sense of movement will also bemovement will also be observed from the other sideobserved from the other side of the fault.of the fault. Strike-SlipStrike-Slip FaultsFaults
Transform FaultsTransform FaultsTransform Faults:Transform Faults: Are aAre a type of strike-slip faulttype of strike-slip fault (defined by Wilson 1965).(defined by Wilson 1965). They form due toThey form due to thethe differences in motiondifferences in motion between lithosphericbetween lithospheric plates.plates. They areThey are basically occur wherebasically occur where type of plate boundarytype of plate boundary is transformed intois transformed into anotheranother.. Main types of transformMain types of transform faults arefaults are::  Ridge-RidgeRidge-Ridge  Ridge-ArcRidge-Arc  Arc-ArcArc-Arc
Other types of faultOther types of fault  en-echelon faults:en-echelon faults: Faults thatFaults that are approximately parallel oneare approximately parallel one another but occur in shortanother but occur in short unconnected segments, andunconnected segments, and sometimes overlapping.sometimes overlapping.  Radial faults:Radial faults: faults that arefaults that are converge toward one pointconverge toward one point  Concentric faults:Concentric faults: faults that arefaults that are concentric to a point.concentric to a point.  Bedding faults (bedding planeBedding faults (bedding plane faults):faults): follow bedding or occurfollow bedding or occur parallel to the orientation ofparallel to the orientation of bedding planes.bedding planes.
CRITERIA FOR FAULTINGCRITERIA FOR FAULTING  Repetition or omissionRepetition or omission of stratigraphic units asymmetricalof stratigraphic units asymmetrical repetitionrepetition  Displacement of recognizable markerDisplacement of recognizable marker such as fossils,such as fossils, color, composition, texture ..etc.)color, composition, texture ..etc.)..  Truncation of structuresTruncation of structures, beds or rock units., beds or rock units.  Occurrence of fault rocksOccurrence of fault rocks (mylonite or cataclastic or both)(mylonite or cataclastic or both)  Presence of S or C structuresPresence of S or C structures or both, rotated porphyryor both, rotated porphyry clasts and other evidence of shear zone.clasts and other evidence of shear zone.  Abundant veinsAbundant veins, silicification or other mineralization along, silicification or other mineralization along fracture may indicate faulting.fracture may indicate faulting.  Drag UnitsDrag Units appear to be pulled into a fault duringappear to be pulled into a fault during movement (usually within the drag fold and the result ismovement (usually within the drag fold and the result is thrust fault)thrust fault)  Reverse dragReverse drag occurs along listric normal faults.occurs along listric normal faults.  SlickensidesSlickensides and slickenlines along a fault surfaceand slickenlines along a fault surface  Topographic characteristicsTopographic characteristics such as drainges that aresuch as drainges that are controlled by faults and fault scarps.controlled by faults and fault scarps.
conclusion Faults are the geological structure which sometimes causes serious damaging along the fault line. Fault may causes the earthquakes which disturbs constructions ,dams, bridges, buildings and even the whole communities Government must have to stop and banned the construction along the fault line, to save the precious life loses.
References www.eeescience.utoledo.edu Web.njcu.edu/sites Faculty.kfump.edu.sa

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Geological Faults

  • 1. University of Azad Jammu and Kashmir Raja Saad Qamar TOPIC FAULTS
  • 3. FAULT CLASSIFICATION ANDFAULT CLASSIFICATION AND TERMINALOGYTERMINALOGY Faults:Faults: Are fractures that have appreciableAre fractures that have appreciable movement parallel to their plane.movement parallel to their plane. They produced usually by seismicThey produced usually by seismic activity.activity. Understanding faults is useful inUnderstanding faults is useful in design for long-term stability ofdesign for long-term stability of dams, bridges, buildings and powerdams, bridges, buildings and power plants. The study of fault helpsplants. The study of fault helps understand mountain building.understand mountain building.
  • 4. Parts of the FaultParts of the Fault Fault planeFault plane: Surface that the movement hasSurface that the movement has taken place within the fault.On this surfacetaken place within the fault.On this surface the dip and strike of the fault is measured.the dip and strike of the fault is measured.  Hanging wall:Hanging wall: The rock mass resting on theThe rock mass resting on the fault plane.fault plane.  Footwall:Footwall: The rock mass beneath the faultThe rock mass beneath the fault plane.plane.  Slip:Slip: Describes the movement parallel to theDescribes the movement parallel to the fault plane.fault plane.  Dip slip: Describes the up and downDip slip: Describes the up and down movement parallel to the dip direction of themovement parallel to the dip direction of the fault.fault.  Strike slip:Strike slip: Applies where movement isApplies where movement is parallel to strike of the fault plane.parallel to strike of the fault plane.  Oblique slip:Oblique slip: Is a combination of strike slipIs a combination of strike slip and dip slip.and dip slip.  Net slip (true displacement): Is the totalNet slip (true displacement): Is the total amount of motion measured parallel to theamount of motion measured parallel to the direction of motiondirection of motion
  • 5.  Separation:Separation: The amount ofThe amount of apparent offset of a faultedapparent offset of a faulted surface, measured in specifiedsurface, measured in specified direction. There are strikedirection. There are strike separation, dip separation, andseparation, dip separation, and net separation.net separation.  Heave:Heave: The horizontalThe horizontal component of dip separationcomponent of dip separation measured perpendicular to strikemeasured perpendicular to strike of the fault.of the fault.  Throw:Throw: The vertical componentThe vertical component measured in vertical planemeasured in vertical plane containing the dip.containing the dip.
  • 6. Features on the fault surfaceFeatures on the fault surface  GroovesGrooves (parallel to the(parallel to the movement direction)movement direction)  Growth of fibrous mineralsGrowth of fibrous minerals (parallel to the movement(parallel to the movement direction)direction)  SlickensidesSlickensides are the polishedare the polished fault surfaces.fault surfaces.  Small steps.Small steps. All are considered a kind ofAll are considered a kind of lineation. They indicate thelineation. They indicate the movement relative trend NW,movement relative trend NW, NE … etc.NE … etc. Small steps may also be used toSmall steps may also be used to determine the movementdetermine the movement direction and direction ofdirection and direction of movement of the opposingmovement of the opposing wall. Slicklines usuallywall. Slicklines usually record only the last momentrecord only the last moment event on the fault.event on the fault.
  • 7. ANDERSON FAULTS CLASSIFICATIONANDERSON FAULTS CLASSIFICATION Anderson (1942) definedAnderson (1942) defined three types of faults:three types of faults:  Normal FaultsNormal Faults  Thrust FaultsThrust Faults  Wrench FaultsWrench Faults (strike slip)(strike slip)
  • 9. Normal FaultNormal Fault Normal Fault: The hanging wall has moved down relative to the footwall. Graben:Graben: consists of a block that has dropped downconsists of a block that has dropped down between two subparllel normal faults that dip towardsbetween two subparllel normal faults that dip towards each other.each other. HorstHorst :: consists of two subparallel normal faults that dipconsists of two subparallel normal faults that dip away from each other so that the block between the twoaway from each other so that the block between the two faults remains high.faults remains high. Listric:Listric: are normal faults that frequently exhibit (concave-are normal faults that frequently exhibit (concave- up) geometry so that they exhibit steep dip near surfaceup) geometry so that they exhibit steep dip near surface and flatten with depth.and flatten with depth. Normal faults usually found in areas where extensional stress isNormal faults usually found in areas where extensional stress is presentpresent..
  • 11. Thrust FaultThrust Fault Thrust 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 usuallyThrust faults usually formed in areas offormed in areas of comperssional stress.comperssional stress. Thrust FaultThrust Fault
  • 13. Strike-Slip FaultStrike-Slip Fault Strike-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 ofNote that the same sense of movement will also bemovement will also be observed from the other sideobserved from the other side of the fault.of the fault. Strike-SlipStrike-Slip FaultsFaults
  • 14. Transform FaultsTransform FaultsTransform Faults:Transform Faults: Are aAre a type of strike-slip faulttype of strike-slip fault (defined by Wilson 1965).(defined by Wilson 1965). They form due toThey form due to thethe differences in motiondifferences in motion between lithosphericbetween lithospheric plates.plates. They areThey are basically occur wherebasically occur where type of plate boundarytype of plate boundary is transformed intois transformed into anotheranother.. Main types of transformMain types of transform faults arefaults are::  Ridge-RidgeRidge-Ridge  Ridge-ArcRidge-Arc  Arc-ArcArc-Arc
  • 15. Other types of faultOther types of fault  en-echelon faults:en-echelon faults: Faults thatFaults that are approximately parallel oneare approximately parallel one another but occur in shortanother but occur in short unconnected segments, andunconnected segments, and sometimes overlapping.sometimes overlapping.  Radial faults:Radial faults: faults that arefaults that are converge toward one pointconverge toward one point  Concentric faults:Concentric faults: faults that arefaults that are concentric to a point.concentric to a point.  Bedding faults (bedding planeBedding faults (bedding plane faults):faults): follow bedding or occurfollow bedding or occur parallel to the orientation ofparallel to the orientation of bedding planes.bedding planes.
  • 16. CRITERIA FOR FAULTINGCRITERIA FOR FAULTING  Repetition or omissionRepetition or omission of stratigraphic units asymmetricalof stratigraphic units asymmetrical repetitionrepetition  Displacement of recognizable markerDisplacement of recognizable marker such as fossils,such as fossils, color, composition, texture ..etc.)color, composition, texture ..etc.)..  Truncation of structuresTruncation of structures, beds or rock units., beds or rock units.  Occurrence of fault rocksOccurrence of fault rocks (mylonite or cataclastic or both)(mylonite or cataclastic or both)  Presence of S or C structuresPresence of S or C structures or both, rotated porphyryor both, rotated porphyry clasts and other evidence of shear zone.clasts and other evidence of shear zone.  Abundant veinsAbundant veins, silicification or other mineralization along, silicification or other mineralization along fracture may indicate faulting.fracture may indicate faulting.  Drag UnitsDrag Units appear to be pulled into a fault duringappear to be pulled into a fault during movement (usually within the drag fold and the result ismovement (usually within the drag fold and the result is thrust fault)thrust fault)  Reverse dragReverse drag occurs along listric normal faults.occurs along listric normal faults.  SlickensidesSlickensides and slickenlines along a fault surfaceand slickenlines along a fault surface  Topographic characteristicsTopographic characteristics such as drainges that aresuch as drainges that are controlled by faults and fault scarps.controlled by faults and fault scarps.
  • 17. conclusion Faults are the geological structure which sometimes causes serious damaging along the fault line. Fault may causes the earthquakes which disturbs constructions ,dams, bridges, buildings and even the whole communities Government must have to stop and banned the construction along the fault line, to save the precious life loses.