FAULTSBy: Andrea Jimeno Martinez

4ºA

Introduction : Definition Types of faults with examples

Normal faultReverse faultStrike - Slip fault

Parts of a fault

Definition: A fault is a planar fracture or discontinuity

in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth's crust result from the action of tectonic forces. Energy release associated with rapid movement on active faults is the cause of most earthquakes.

Types of faults

Normal fault (slide) Reverse fault (jump) Strik-slip

Normal fault A normal fault is a dip-slip fault in which the block above

the fault has moved downward relative to the block below. The hanging wall has slipped down in comparison to the foot wall.  Gravity causes the hanging wall to slip down. Normal Faults are from layers being pulled apart. 

Examples Normal faults generally occur in places where the

lithosphere is being stretched. Consequently they are the chief structural components of many sedimentary rift basins where they have major significance for hydrocarbon exploration. E.g. the North Sea.

Reverse fault A reverse fault is a dip-slip fault in which the upper block,

above the fault plane, moves up and over the lower block. This type of faulting is common in areas of compression, such as regions where one plate is being sub ducted under another.

The hanging wall has slipped up in comparison to the foot wall.

When layers are pushed together this is the kind of fault that occurs.

Examples  A reverse fault occurs primarily across lithological units

where as a thrust usually occurs within or at a low angle to lithological units. It is often hard to recognize thrusts because their deformation and dislocation can be difficult to detect when they occur within the same rocks without appreciable offset of lithological contacts.

The Sierra Madre fault zone of southern California is an example of reverse-fault.

Strike-slip fault A strike-slip fault is a fault on which the two blocks slide

past one another. These faults are identified as either right-lateral or left lateral depending on whether the displacement of the far block is to the right or the left when viewed from either side.

Examples Transform faults within continental plates include some of

the best known examples of strike-slip structures, such as the San Andreas Fault, the Dead Sea Transform, the North Anatolian Fault and the Alpine Fault. The San Andreas Fault in California is an example of a right lateral fault:

Parts of a fault

SummaryType of fault Type of force Vertical or

horizontal motion

Type of plate boundary

Type of Earthquackes

Normal Tension Vertical Divergent Shallow & intermediate

Reverse Compression Vertical Convergent All types

Strike-slip Shearing Horizontal Transform Shallow

THE END