Geology 360 - Geology 360 - Introduction to Strike-Slip Introduction to Strike-Slip Faults Faults
Dec 20, 2015
Geology 360 - Geology 360 - Introduction to Strike-Slip FaultsIntroduction to Strike-Slip Faults
Levant Strike-Slip FaultsLevant Strike-Slip Faults
Left-lateral strike-slip Levant fault, plate
boundary between Arabia and Africa
San Andreas San Andreas from Spacefrom Space
San Francisco Bay, California.
Two northwest-southeast-trending faults are visible.
The Hayward Fault, bordering the urban area east of San Francisco Bay
The San Andreas Fault, crossing the mid-San Francisco Peninsula before dipping beneath the Pacific Ocean and surfacing again northwest of Golden Gate Bridge
San Andreas fault, San Andreas fault,
western North Americawestern North America
OutlineOutline
• Stick-Slip and Creep
• Andersonian Theory
• Kinematics
• Strike-Slip Faults on Continental Margins
• Strike-Slip Faults on Mid-Ocean Ridges
Stick-Slip: Elastic Rebound TheoryStick-Slip: Elastic Rebound Theory
Elastic Rebound TheoryElastic Rebound Theory
• Imagine a fence across an active Imagine a fence across an active
faultfault
Elastic Rebound TheoryElastic Rebound Theory
• Imagine a fence across an active Imagine a fence across an active
faultfault
• Regional deformation occurs but Regional deformation occurs but
the fault does not break. The the fault does not break. The
fence becomes curved.fence becomes curved.
Elastic Rebound TheoryElastic Rebound Theory
• Imagine a fence across an active Imagine a fence across an active
faultfault
• Regional deformation occurs but Regional deformation occurs but
the fault does not break (locked the fault does not break (locked
fault) fault)
•Once the fault breaks, the fence Once the fault breaks, the fence
is sheared in half and marks offsetis sheared in half and marks offset
•The far-field strain may limit The far-field strain may limit
whether the fault accommodates whether the fault accommodates
all the plate motion at its traceall the plate motion at its trace
Elastic Rebound TheoryElastic Rebound Theory
Elastic Rebound TheoryElastic Rebound Theory
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Creep (Aseismic Slip)Creep (Aseismic Slip)
• Imagine a fence across an active Imagine a fence across an active
faultfault
• Slip occurs slowly on the fault Slip occurs slowly on the fault
continually over time (fault is not continually over time (fault is not
locked)locked)
• Creeping faults do not store Creeping faults do not store
elastic energy that might be elastic energy that might be
released by a stick-slip event (an released by a stick-slip event (an
earthquake)earthquake)
Andersonian TheoryAndersonian Theory
Conjugate Strike-Slip Conjugate Strike-Slip
FaultsFaults
Determining Sense of SlipDetermining Sense of Slip
Right-Lateral (Dextral)Right-Lateral (Dextral)
Left-Lateral (Sinistral)Left-Lateral (Sinistral)
Arrow Heads ( ) and Tails ( )Arrow Heads ( ) and Tails ( )
Block moving toward you like an arrowhead Block moving toward you like an arrowhead
heading towards youheading towards you
Block moving away from you like seeing the Block moving away from you like seeing the
feathers of an arrow feathers of an arrow
Arrow Heads ( ) and Tails ( )Arrow Heads ( ) and Tails ( )
Right-lateral or left-lateral?Right-lateral or left-lateral?
Arrow Heads ( ) and Tails ( )Arrow Heads ( ) and Tails ( )
Left-lateralLeft-lateral
Arrow Heads ( ) and Tails ( )Arrow Heads ( ) and Tails ( )
Sinistral or Dextral?Sinistral or Dextral?
Arrow Heads ( ) and Tails ( )Arrow Heads ( ) and Tails ( )
DextralDextral
Strike-Slip Faulting: Shallow Brittle vs Deep Strike-Slip Faulting: Shallow Brittle vs Deep
ShearShear
Strike-Slip Faulting: EQ’s = dislocationsStrike-Slip Faulting: EQ’s = dislocations
http://www.data.scec.org/Module/links/landrupt.html
Landers rupture propagation movies
Strike-Slip Faulting: EQ’s = dislocationsStrike-Slip Faulting: EQ’s = dislocations
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Strike-Slip Faulting: EQ’s = dislocationsStrike-Slip Faulting: EQ’s = dislocations
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Strike-Slip Faults on Continental Strike-Slip Faults on Continental
MarginsMargins
What is the sense of slip?What is the sense of slip?
N50 m
Strike-Slip Faults on Continental Strike-Slip Faults on Continental
MarginsMargins
Right-lateral (dextral)Right-lateral (dextral)
N50 m
TranstensionTranstension
Development of a Pull-Apart Development of a Pull-Apart
BasinBasin
Pull-Apart BasinPull-Apart Basin
Initial Releasing BendInitial Releasing Bend
Evolution of a Releasing Evolution of a Releasing
BendBend
Normal (-) Flower Structure - Normal (-) Flower Structure -
Tulip Tulip
TranspressionTranspression
Development of a Restraining Development of a Restraining
BendBend
Development of a Restraining Development of a Restraining
BendBend
Initial Restraining BendInitial Restraining Bend
Evolution of a Restraining Evolution of a Restraining
BendBend
Reverse (+) Flower Structure - Reverse (+) Flower Structure -
PalmPalm
Summary of Flower Structures - Palms Summary of Flower Structures - Palms
& Tulips& Tulips
Summary of Step Overs - Strike-Slip Summary of Step Overs - Strike-Slip
FaultsFaults
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Los Angeles - Pull apart structureLos Angeles - Pull apart structure
Releasing Releasing bendbend
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Summary of Flower Structures - Palms Summary of Flower Structures - Palms
& Tulips& Tulips
Summary of Flower Structures - Palms Summary of Flower Structures - Palms
& Tulips& Tulips
Summary of Flower Structures - Palms Summary of Flower Structures - Palms
& Tulips& Tulips
Summary of Flower Structures - Palms Summary of Flower Structures - Palms
& Tulips& Tulips
Oceanic Strike Slip fault: TransformsOceanic Strike Slip fault: Transforms
Strike-Slip Faults on Mid-Ocean Strike-Slip Faults on Mid-Ocean
RidgesRidges
What is the sense of slip?What is the sense of slip?
Strike-Slip Faults on Mid-Ocean Strike-Slip Faults on Mid-Ocean
RidgesRidges
Right-lateral (Dextral)Right-lateral (Dextral)
Pacific-Antarctic RidgePacific-Antarctic Ridge
Magnetic anomalies from present to 9.9 MaMagnetic anomalies from present to 9.9 Ma
Warm colors indicate positive polarityWarm colors indicate positive polarity
Cool colors indicate reverse polarityCool colors indicate reverse polarity