Faults and Faulting

Regional Strain

Types of Fault and the Principal Stresses

Fault Rocks

• Gouge: non-cohesive, fine grained• Breccia: coarse angular fragments• Cataclasite: cohesive fragments• Fault Melt (pseudotachylite):

– due to friction• Mylonite: ductile-brittle fault zone

Fault scarp after an earthquake- Nevada

Fault Striations- Slickenlines

Fault zone breccia

in QuartziteBrooks Range,

AK

Hydrothermal Fault BrecciaHydrothermal Fault Breccia

Fault Melt

Fault Melt

Mylonites

Evolution of an ActiveMountain

Front

New Mountains-Active Fault –Basin and Range Province

Slot Canyon, Faulted Alluvial Fan- Death Valley

Some Faults are Almost flat

Faults in Reflection Seismic Data- Hope Basin, AK

Interpreted Seismic Data

3 km

0

The longer a fault, the more displacement

it has

Faults Symbols in Map View

Normal Faults

Thrust Faults

Decorations are on the hanging wall

Fault on a Geological Map

Map View of FaultsSlip vs. Separation

Separation : 2DIf layers are tilted it may be deceiving

These are two dipping dikes that are faulted. What kind of fault is this?