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Geology 3120 -Introduction to Strike-Slip Faults

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Outline Stick-Slip and Creep Andersonian Theory Kinematics Strike-Slip Faults on Continental Margins Strike-Slip Faults on Mid-Ocean Ridges

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Elastic Rebound Theory Imagine a fence across an activefault

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Elastic Rebound Theory Imagine a fence across an activefault Regional deformation occurs butthe fault does not break. The

fence becomes curved.

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Elastic Rebound Theory Imagine a fence across an active fault

Regional deformation occurs but thefault does not break.

Once the fault breaks, the fence issheared in half and marks offset

Note that far-field strain may limitwhether the fault accommodates all the

plate motion at its trace

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Creep (Aseismic Slip) Imagine a fence across an active fault

Slip occurs slowly on the faultcontinually over time.

Creeping faults do not store elasticenergy that might be released by

a stick-slip event (an earthquake)

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A short portion of the San Andreas fault creeps(Hollister California sits across the fault)

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Determining Sense of Slip

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Right-Lateral (Dextral)

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Left-Lateral (Sinistral)

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Arrow Heads ( ) and Tails ( )

Block moving toward you like an arrowhead

heading towards youBlock moving away from you like seeing the

feathers of an arrow

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Arrow Heads ( ) and Tails ( )

! Right-lateral or left-lateral?

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Arrow Heads ( ) and Tails ( )

! Left-lateral

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Arrow Heads ( ) and Tails ( )

! Sinistral or Dextral?

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Arrow Heads ( ) and Tails ( )

! Dextral

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Strike-Slip Faulting: EQs = dislocationsSee http://www.data.scec.org/Module/links/landrupt.html

Landers rupture propagation movies

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Strike-Slip Faults on Continental Margins

! Right-lateral (dextral)

N50 m

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Transtension

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Pull-Apart Basin

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Initial Releasing Bend

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Evolution of a Releasing Bend

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Normal (-) Flower Structure - Tulip

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Transpression

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Development of a Restraining Bend

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Initial Restraining Bend

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Evolution of a Restraining Bend

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Reverse (+) Flower Structure - Palm

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Summary of Flower Structures - Palms Tulips

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Oceanic Strike Slip fault: Transforms

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Strike-Slip Faults on Mid-Ocean Ridges

! What is the sense of slip?

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Strike-Slip Faults on Mid-Ocean Ridges

! Right-lateral (Dextral)

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Transfer Faults allowsimultaneous movement andequal strain on separatedstructures.

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Partitioned strike slip Oblique subduction thrust beltbacked by strike slip faults Sumatra is the perfect example

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Partitioned strike slip Oblique subduction thrust beltbacked by strike slip faults Sumatra is the perfect example

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Partitioned strike slip Oblique subduction thrust beltbacked by strike slip faults Sumatra is the perfect example

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Indentor tectonicsContinental collision

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Elastic stress transferWhatr defines shaking(magnitude, proximity, whatrock is the structure built on(hard better than soft)

Discuss elastic stresstransfer