Faults, fault zones, shear zones...

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1 Faults and Faulting Geol342 2008 Many diagrams are from Earth Structure, van der Pluijm and Marshak, 2004 Topics Faults on outcrop, maps, and cross sections Fault zones and fault rocks Types of faults and terminology Slip vs separation Faults in wells Fault propagation Faults, fault zones, shear zones Terminology Hanging wall Foot wall Fault Zone in Granitic Gneiss Fault scarp after an earthquake- Nevada

Transcript of Faults, fault zones, shear zones...

Page 1: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Faults and Faulting

Geol342

2008Many diagrams are from Earth Structure, van der Pluijm and Marshak, 2004

Topics

• Faults on outcrop, maps, and cross sections• Fault zones and fault rocks• Types of faults and terminology• Slip vs separation• Faults in wells• Fault propagation

Faults, fault zones, shear zones Terminology

Hanging wall

Foot wall

Fault Zone in Granitic Gneiss

Fault scarp after an earthquake- Nevada

Page 2: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Plate Boundary-San Andreas Fault

Fault

Fence

Fault zone in Quartzites-Brooks Range

Small Normal Faults

Small Thrust Fault – Moss Beach, Ca

Types of fault

Oblique slip

Page 3: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Fault Striations- Slikenlines

Regional Strain

Types of Fault and the Principal Stresses

Normal Thrust Strike-slip

Fault rocks with depth Fault Rocks

• Gauge: non-cohesive, fine grain• Breccia: coarse angular fragments• Cataclasite: cohesive fragments• Mylonite: ductile-brittle fault zone

Depth

Page 4: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Fault zone breccia

in QuartziteBrooks Range,

AK

Hydrothermal Fault Breccia

Fault Melt

Mylonites

Undeformed granite Deformed

Young Mountains-Active Fault –Basin and Range Province

Page 5: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Evolution of an ActiveMountain

Front

Triangular Facets on an active Mountain Front

Faults Symbols in Map View

Normal Faults

Thrust Faults

Decorations are on the hanging wall

Strike-slip

Fault on a Geological Map

What kind of fault is this?North

Map View of FaultsSlip vs. Separation

Page 6: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Block Diagram

How is this possible?

Some Faults are Almost flatFaults in Seismic Reflection Data- Hope Basin, AK

Interpreted Seismic Data

3 km

0

Faulted structure contour map

Page 7: Faults, fault zones, shear zones Terminologypages.geo.wvu.edu/~jtoro/structure/ppt342/10faults-342.pdf · Strike-slip Fault on a Geological Map What kind of fault is this? North Map

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Faults from well dataFaults are shear fractures

in an elastic solid

Fault Propagation

• Right-lateral Coulomb stress change on planes parallel to the main fault (Stein and Lisowski, 1983).

The longer a fault, the more displacement

it has